user157: When attend an event at the sangha I'm with (Triratna) we often transfer merit (puñña) at the end of it. So any good result of the meditation, ritual, dharma study etc... we give away. I know that this isn't something we have just invented. It's a practice that we have taken from other traditions.
What confuses me is merit can be given away. If merit is the fruits of my karma in what sense can this be transferred over to another being? How can someone else benefit from my skillful actions?

user832: first what is merit
http://en.wikipedia.org/wiki/Merit_(Buddhism)

It is that which accumulates as a result of good deeds, acts, or
  thoughts and which carries over throughout the life or the subsequent
  incarnations.

One approach toward merit is that it is like an award or increase in the ledger (chinese see link above) - these are both difficult things to give away because we are not able to touch them or even be sure they are really there.
Another idea about merit is that it is the feeling and awareness of the Buddha nature that results from meditation, helping others, offering or dedicating the fruits of our life and consciousness to helping others.
The reason that makes sense to me is that we give or offer this type of merit to all sentient beings because this brings us closer to the intentions of the Buddha nature, to help all and ask for nothing.

user9965: Here the question has been asked: how can merit be transferred?
But most of the commentators are commented out of the question. do not say how to transfer or whether merit can be transferred or not. 
What are the main differences between Theravada and Mahayana?
Answer: There are three main differences between Theravada and Mahayana. they are as follows: the Mahayana strongly believe that the Buddha nature, Bodhisattva path and Transfer of Merit.  which Theravada does not follows.     

user533: What I have learned from Theravada tradition (based on a Buddha's discourse) is that you can only transfer merits to beings in the hungry ghost realm, if a relative of yours has passed away and you have reasons to believe he/she is in the ghost realm (manifestations, signs etc.*) you can burn food, incense, clothes or donate food and clothes to the sangha transferring the merits to him/her.
*Many buddhist traditions (especially chinese) believe that circa 1 week after a relative has passed away he comes back looking for food and clothes if he/she is in the ghost realm, of course the natural thing to do is look for the relatives in the human realm to support them.
PS: After meditation sessions it is common to dedicate the merits to someone, however I think this is slightly different from actually transferring the merits.

user43: The first paramita in Mahayana is paramita of generosity. And what generosity could we talk about if we are keeping our merit to ourselves? 
As many Buddhist practices, this transfer of merit thing works on multiple levels.
One of them is prophylactics against spiritual materialism. You don't want to get caught up in the idea of accumulating anything for your ego to feed on. In some sense Satdharma is about becoming a very decent, very sane person, like a very lucid grandma. This grandma does not dream of career or wealth or popularity anymore, she does not want to learn Haskell because it's so cool, she just clearly knows that to be a decent person, rather than being full of yourself, you have to keep your eyes open and only do what makes sense. So instead of assuming this notion of accumulation, you could say: "Ok, what else do I need to drop?"
Aside from giving away one's merit there is also a parallel practice: of taking on blame -- if you pay attention you can feel how both of these relieve the energy tension. You could say these two are quintessential Mahayana practices towards starving the ego. The same idea is utilized in Tonglen meditation: we breath in all the suffering of the world and breath out happiness, for all sentient beings to enjoy. Another similar practice is e.g. when you're cold, to wish that you are taking on a piece of suffering some unfortunate beings experience in the Freezing Hell, and when you are spacing out in front of the fireplace to send that happiness to all spaces and times that need it.
This is all part of Bodhicitta, generating Buddha's mindset.

user289: This originated in the observation that to rejoice in other successes was a virtuous deed. So if I did something well, in the Buddhist sense, I don't know, maybe I ordained into the sangha, I could send you a post card and you would be happy to know about it. At that point my merit lead to you gaining more merit. (Wikipedia said so, I don't have the link at the moment)
That sort of merit transfer eventually turned into a semi-magical substance you could earn and donate to the needy like money.
I don't know if it has any support, but I see it as sort of a practice that allows one to not take credit for what good things you've done (especially if you are surrounded by people with fragile egos who feel bad whenever they see someone more accomplished then themselves) and if you have a Mahayana bent, to refocus on why you were doing meritorious things-- i.e. we do meritorious things to gain enlightenment, but we're not enlightened until everyone is enlightened. 

user5323: According to the Theravadian Buddhist tradition, I find it difficult to fathom the principle of accumulating 'Merit' or 'Punya kamma', as well as the popular practice of transferring 'merits' to one's departed loved ones.
Like many other things in Buddhist practices and rituals, 'Punya kamma' also has the hallmark of a vestigial remnant of Hinduism.
Accumulation of merit has minimal input on purification of one's mind, which is the cornerstone of the Buddha-dhamma. There is mystic and a degree of 'lobha' when one collect merits hoping a better life, as practised and often preached today. Secondly, why make a case for one's relatives as there supposed to be 'No Self'?

user-1: Here is a quote on the transfer of merit. Its discussed what the benefits are and how the transfer is done. The quote is from the book "What Buddhists Believe" by Ven. K. Sri Dhammananda, p. 409-410:

The Significance of Transference of Merits to the Departed
"ACCORDING to Buddhism, good deeds or ‘acts of merit’ bring happiness to the doer both in this world and in the hereafter. Acts of merit are also believed to lead towards the final goal of everlasting happiness. The acts of merit can be performed through body, speech or mind. Every good deed produces ‘merit’ (store of positive spiritual well being) which accumulates to the ‘credit’ of the doer. Buddhism also teaches that the acquired merit can be transferred to others; it can be shared vicariously with others. In other words, the merit is ‘transferable’ and so can be shared with other persons. The persons who receive the merit can be either living or departed ones.
The method for transferring merits is quite simple. First some good deeds are performed. The doer of the good deeds has merely to wish that the merit gained accrues to someone in particular. This wish can be purely mental or it can be accompanied by an expression of words.
The wish could be made with the beneficiary being aware of it. When the beneficiary is aware of the act or wish, then a mutual ‘rejoicing in’ merit takes place. Here the beneficiary becomes a participant of the original deed by associating him or herself with the deed done. If the beneficiary identifies him or herself with both the deed and the doer, he or she can sometimes acquire even greater merit than the original doer, either because the elation is greater or because the appreciation of the value of the deed is based on an understanding of Dharma. Buddhist texts contain several stories of such instances.
The ‘joy of transference of merits’ can also take place with or without the knowledge of the doer of the meritorious act. All that is necessary is for the beneficiary to feel gladness in the heart when he or she becomes aware of the good deed. If one wishes, one can express joy by saying ‘sadhu’ which means ‘well done’. What is being done is creating a kind of mental or verbal applause. In order to share the good deed done by another, what is important is that there must be actual approval of the deed and joy arising in the beneficiary’s heart.
  Even if so desired, the doer of a good deed cannot prevent another’s ‘rejoicing in the merit’ because he or she has no power over another’s thoughts. According to the Buddha, in all actions, thought is what really matters. Transference is primarily an act of the mind.
To transfer merit does not mean that a person is deprived of the merit originally acquired from his or her good deed. On the contrary, the very act of ‘transference’ is a good deed in itself and hence enhances the merit already earned".

Edit: Here is a audio dhamma talk on the 10 pāramīs by Ven. Bhikkhu Bodhi. The first perfection of giving might provide further information to your question.

user9965: The merit cannot be transferred through anyway to the passed one or man to man. But the merit can be shared to the departed one and also man to man. In the Tirokuddo Sutta, has no mentioned that the merit can be transferred to passed one or others. in this Sutta, in the last verse, the word 'puñña's has mentioned but that is acquired by the donor himself. 
In the Nidāna of this sutta, has referred that the deceased person Peta (Ghost) can say the word, (Sadhu-3x). The word sadhu means well-done, share (Anumodana), can say 3 times by the Paradattabhojhi peta that is why they can earn merit themselves, I think it is crucially important to introduce here about the peta realm. In the peta world, there are 40 types of petas but, among them, only a type  of peta can earn merit based on who share through their relatives and the rest of  39 types of petas never get the chance to earn merit from their relatives because they are unable to utter the word (Sadhu). When the ghost's relatives accomplish virtuous activities then they respectfully utter sadhu 3 times by pouring water, at the same time the ghost enable to appreciate sadhu 3 times, that means after saying the word 'sadhu' the ghosts earn merit themselves, when the ghosts earn merit then the ghosts can be freed from ghosts lives. It is not the true fact that they receive the donor's transferring merit. The ghost acquires merits themselves through uttering the word Sadhu thrice. Here I can give a parallel of sharing: if a person lights a candle, then you also wish to delight your candle but, you have no lighter to lighting it, then other shares his candle's fire from his candle and you lighted your candle. When you took at the fire by comparing from others candle, then both candle's flems are similar. It is called the 'sharing', in this way merit can be shared to others but, merit cannot be Transferred to others. Buddhism never says merit can be transferred, it's only possible to share. Those who proclaim that the merit can transfer please cite the reference in where did the Buddha say in Tipitaka. Thank you.     

user295: The mechanism behind merit transfer is this:

There is an element of Metta which benefits one self and other as it creates positive vibes. When you do good followed by strong volition to share this positivity this creates more positivity. Also this vibes can be sometimes telepathic.
Also being in some other realms (not all realms even then not always) can sense any positive vibes when we give Metta or think about then strongly (quasi telepathic). So when you recall a deceased person sometimes this becomes like a ping. If the other being develops appreciative joy in his mind to the actions that was done this itself creates the merit in the merit transfer.

So the traster has two elements:

Positive vibes you create around you has positive effects to others beings around
Appreciative joy of good and commendable action of others create positive mental Karma for the beings who do so

This instruments the merit transfer process.

157: <p>When attend an event at the sangha I'm with (<a href="https://thebuddhistcentre.com/text/what-triratna-buddhist-community" rel="nofollow">Triratna</a>) we often transfer merit (puñña) at the end of it. So any good result of the meditation, ritual, dharma study etc... we give away. I know that this isn't something we have just invented. It's a practice that we have taken from other traditions.</p>

<p>What confuses me is merit can be given away. If merit is the fruits of my karma in what sense can this be transferred over to another being? How can someone else benefit from my skillful actions?</p>
 832: <p>first what is merit
<a href="http://en.wikipedia.org/wiki/Merit_(Buddhism)" rel="nofollow">http://en.wikipedia.org/wiki/Merit_(Buddhism)</a></p>

<blockquote>
  <p>It is that which accumulates as a result of good deeds, acts, or
  thoughts and which carries over throughout the life or the subsequent
  incarnations.</p>
</blockquote>

<p>One approach toward merit is that it is like an award or increase in the ledger (chinese see link above) - these are both difficult things to give away because we are not able to touch them or even be sure they are really there.</p>

<p>Another idea about merit is that it is the feeling and awareness of the Buddha nature that results from meditation, helping others, offering or dedicating the fruits of our life and consciousness to helping others.</p>

<p>The reason that makes sense to me is that we give or offer this type of merit to all sentient beings because this brings us closer to the intentions of the Buddha nature, to help all and ask for nothing.</p>
 9965: <p>Here the question has been asked: how can merit be transferred?</p>

<p>But most of the commentators are commented out of the question. do not say how to transfer or whether merit can be transferred or not. </p>

<p>What are the main differences between Theravada and Mahayana?
Answer: There are three main differences between Theravada and Mahayana. they are as follows: the Mahayana strongly believe that the Buddha nature, Bodhisattva path and Transfer of Merit.  which Theravada does not follows.     </p>
 533: <p>What I have learned from Theravada tradition (based on a Buddha's discourse) is that you can only transfer merits to beings in the hungry ghost realm, if a relative of yours has passed away and you have reasons to believe he/she is in the ghost realm (manifestations, signs etc.*) you can burn food, incense, clothes or donate food and clothes to the sangha transferring the merits to him/her.</p>

<p>*Many buddhist traditions (especially chinese) believe that circa 1 week after a relative has passed away he comes back looking for food and clothes if he/she is in the ghost realm, of course the natural thing to do is look for the relatives in the human realm to support them.</p>

<p>PS: After meditation sessions it is common to dedicate the merits to someone, however I think this is slightly different from actually transferring the merits.</p>
 43: <p>The first paramita in Mahayana is paramita of generosity. And what generosity could we talk about if we are keeping our merit to ourselves? </p>

<p>As many Buddhist practices, this transfer of merit thing works on multiple levels.</p>

<p>One of them is prophylactics against spiritual materialism. You don't want to get caught up in the idea of accumulating anything for your ego to feed on. In some sense Satdharma is about becoming a very decent, very sane person, like a very lucid grandma. This grandma does not dream of career or wealth or popularity anymore, she does not want to learn Haskell because it's so cool, she just clearly knows that to be a decent person, rather than being full of yourself, you have to keep your eyes open and only do what makes sense. So instead of assuming this notion of accumulation, you could say: "Ok, what else do I need to drop?"</p>

<p>Aside from giving away one's merit there is also a parallel practice: of taking on <em>blame</em> -- if you pay attention you can feel how both of these relieve the energy tension. You could say these two are quintessential Mahayana practices towards starving the ego. The same idea is utilized in Tonglen meditation: we breath in all the suffering of the world and breath out happiness, for all sentient beings to enjoy. Another similar practice is e.g. when you're cold, to wish that you are taking on a piece of suffering some unfortunate beings experience in the Freezing Hell, and when you are spacing out in front of the fireplace to send that happiness to all spaces and times that need it.</p>

<p>This is all part of Bodhicitta, generating Buddha's mindset.</p>
 289: <p>This originated in the observation that to rejoice in other successes was a virtuous deed. So if I did something well, in the Buddhist sense, I don't know, maybe I ordained into the sangha, I could send you a post card and you would be happy to know about it. At that point my merit lead to you gaining more merit. (Wikipedia said so, I don't have the link at the moment)</p>

<p>That sort of merit transfer eventually turned into a semi-magical substance you could earn and donate to the needy like money.</p>

<p>I don't know if it has any support, but I see it as sort of a practice that allows one to not take credit for what good things you've done (especially if you are surrounded by people with fragile egos who feel bad whenever they see someone more accomplished then themselves) and if you have a Mahayana bent, to refocus on why you were doing meritorious things-- i.e. we do meritorious things to gain enlightenment, but we're not enlightened until everyone is enlightened. </p>
 5323: <p>According to the Theravadian Buddhist tradition, I find it difficult to fathom the principle of accumulating 'Merit' or 'Punya kamma', as well as the popular practice of transferring 'merits' to one's departed loved ones.</p>

<p>Like many other things in Buddhist practices and rituals, 'Punya kamma' also has the hallmark of a vestigial remnant of Hinduism.</p>

<p>Accumulation of merit has minimal input on purification of one's mind, which is the cornerstone of the Buddha-dhamma. There is mystic and a degree of 'lobha' when one collect merits hoping a better life, as practised and often preached today. Secondly, why make a case for one's relatives as there supposed to be 'No Self'?</p>
 -1: <p>Here is a quote on the transfer of merit. Its discussed what the benefits are and how the transfer is done. The quote is from the book <a href="http://www.buddhanet.net/pdf_file/whatbelieve.pdf" rel="nofollow"><em>"What Buddhists Believe"</em></a> by Ven. K. Sri Dhammananda, p. 409-410:</p>

<blockquote>
  <p><strong>The Significance of Transference of Merits to the Departed</strong></p>
  
  <p>"ACCORDING to Buddhism, good deeds or ‘acts of merit’ bring happiness to the doer both in this world and in the hereafter. Acts of merit are also believed to lead towards the final goal of everlasting happiness. The acts of merit can be performed through body, speech or mind. Every good deed produces ‘merit’ (store of positive spiritual well being) which accumulates to the ‘credit’ of the doer. Buddhism also teaches that the acquired merit can be transferred to others; it can be shared vicariously with others. In other words, the merit is ‘transferable’ and so can be shared with other persons. The persons who receive the merit can be either living or departed ones.</p>
  
  <p>The method for transferring merits is quite simple. First some good deeds are performed. The doer of the good deeds has merely to wish that the merit gained accrues to someone in particular. This wish can be purely mental or it can be accompanied by an expression of words.</p>
  
  <p>The wish could be made with the beneficiary being aware of it. When the beneficiary is aware of the act or wish, then a mutual ‘rejoicing in’ merit takes place. Here the beneficiary becomes a participant of the original deed by associating him or herself with the deed done. If the beneficiary identifies him or herself with both the deed and the doer, he or she can sometimes acquire even greater merit than the original doer, either because the elation is greater or because the appreciation of the value of the deed is based on an understanding of Dharma. Buddhist texts contain several stories of such instances.</p>
  
  <p>The ‘joy of transference of merits’ can also take place with or without the knowledge of the doer of the meritorious act. All that is necessary is for the beneficiary to feel gladness in the heart when he or she becomes aware of the good deed. If one wishes, one can express joy by saying ‘sadhu’ which means ‘well done’. What is being done is creating a kind of mental or verbal applause. In order to share the good deed done by another, what is important is that there must be actual approval of the deed and joy arising in the beneficiary’s heart.
  Even if so desired, the doer of a good deed cannot prevent another’s ‘rejoicing in the merit’ because he or she has no power over another’s thoughts. According to the Buddha, in all actions, thought is what really matters. Transference is primarily an act of the mind.</p>
  
  <p>To transfer merit does not mean that a person is deprived of the merit originally acquired from his or her good deed. On the contrary, the very act of ‘transference’ is a good deed in itself and hence enhances the merit already earned".</p>
</blockquote>

<p>Edit: <a href="http://bodhimonastery.org/a-study-of-the-paramis.html" rel="nofollow">Here is a audio dhamma talk on the 10 pāramīs by Ven. Bhikkhu Bodhi. The first perfection of giving might provide further information to your question.</a></p>
 9965: <p>The merit cannot be transferred through anyway to the passed one or man to man. But the merit can be shared to the departed one and also man to man. In the Tirokuddo Sutta, has no mentioned that the merit can be transferred to passed one or others. in this Sutta, in the last verse, the word 'puñña's has mentioned but that is acquired by the donor himself. </p>

<p>In the Nidāna of this sutta, has referred that the deceased person Peta (Ghost) can say the word, (Sadhu-3x). The word sadhu means well-done, share (Anumodana), can say 3 times by the Paradattabhojhi peta that is why they can earn merit themselves, I think it is crucially important to introduce here about the peta realm. In the peta world, there are 40 types of petas but, among them, only a type  of peta can earn merit based on who share through their relatives and the rest of  39 types of petas never get the chance to earn merit from their relatives because they are unable to utter the word (Sadhu). When the ghost's relatives accomplish virtuous activities then they respectfully utter sadhu 3 times by pouring water, at the same time the ghost enable to appreciate sadhu 3 times, that means after saying the word 'sadhu' the ghosts earn merit themselves, when the ghosts earn merit then the ghosts can be freed from ghosts lives. It is not the true fact that they receive the donor's transferring merit. The ghost acquires merits themselves through uttering the word Sadhu thrice. Here I can give a parallel of sharing: if a person lights a candle, then you also wish to delight your candle but, you have no lighter to lighting it, then other shares his candle's fire from his candle and you lighted your candle. When you took at the fire by comparing from others candle, then both candle's flems are similar. It is called the 'sharing', in this way merit can be shared to others but, merit cannot be Transferred to others. Buddhism never says merit can be transferred, it's only possible to share. Those who proclaim that the merit can transfer please cite the reference in where did the Buddha say in Tipitaka. Thank you.     </p>
 295: <p>The mechanism behind merit transfer is this:</p>

<ol>
<li>There is an element of Metta which benefits one self and other as it creates positive vibes. When you do good followed by strong volition to share this positivity this creates more positivity. Also this vibes can be sometimes telepathic.</li>
<li>Also being in some other realms (not all realms even then not always) can sense any positive vibes when we give Metta or think about then strongly (quasi telepathic). So when you recall a deceased person sometimes this becomes like a ping. If the other being develops appreciative joy in his mind to the actions that was done this itself creates the merit in the merit transfer.</li>
</ol>

<p>So the traster has two elements:</p>

<ol>
<li>Positive vibes you create around you has positive effects to others beings around</li>
<li>Appreciative joy of good and commendable action of others create positive mental Karma for the beings who do so</li>
</ol>

<p>This instruments the merit transfer process.</p>
