user10105: I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it? How is Metta properly cultivated as a meditation? As in how to develop the Vitakka Vicara on metta in meditation? 

user-1: If I were you, I'd try the slowest way to samadhi.  Generally, the more results-oriented your meditation is, the worse it's going to go.  

user-1: "I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it?"
Like @Lanka said, I think the fastest way to samadhi is the fastest way you can overcome the five hindrances, and there's a large repertoire of trainings for doing that (e.g.
 here), including metta meditation, mindfulness of the body, meditation on unattractive, etc.
metta is particularly effective as a practice to overcome the presence of anger / ill will.
"How is Metta properly cultivated as a meditation?"
This is the standard description of metta training in the suttas:

a bhikkhu abides pervading one quarter with a mind imbued with loving-kindness, likewise the second, likewise the third, likewise the fourth; so above, below, around, and everywhere, and to all as to himself, he abides pervading the all-encompassing world with a mind imbued with loving-kindness, abundant, exalted, immeasurable, without hostility and without ill will. 

In more detail, one may use specific beings as target of the practice and increase it's range progressively until it's boundless, towards everyone. Or, alternatively, one may use some phrases such as "may all beings be free of enmity, free from affliction, at ease" (I think these are in the Paṭisambhidāmagga).
Or, alternatively, one can arouse a metta attitude and progressively expand it, as per the passage above, irradiating it in one direction after another, making the mind completely immersed in it, all pervading and  boundless. 

Personally, I let many images come to my mind and imagine myself always trying to ease the burden of others, with the desire for them to be well. At this point, I don't usually focus on anyone in particular, as I find this much harder. So these images may be memories or my own imagination -- but I just imagine to the extent that it increases metta, without getting lost on imaginations.
Then, there's a distinct pleasant feeling, both physical and mental, that arises from that. At that point, it's self enforcing, as it seems the mind inclines naturally towards that pleasant feeling. Then I try to expand that metta attitude until I'm completely immersed on it, as per the sutta, progressively to all directions. When I feel completely immersed on it, I abide on that all around irradiating, without focusing on any particular direction. 
So, effectively, I expand it until I become a loving person towards all. In other words, until I feel it becomes my reflex to help others without hesitation, whoever it may be -- so only at this point, when metta is strong, that I try to think of particular persons who I would otherwise find myself having difficulties being good towards them.

user8157: 'Satipatthana' meditation is called 'the direct path' therefore is the fastest path to jhana. 

This is the direct path for the purification of beings, for the overcoming of sorrow & lamentation, for the disappearance of pain &
  distress, for the attainment of the right method & for the realization
  of Unbinding — in other words, the four frames of reference.... There is the case where a monk remains... ardent, clearly comprehending & mindful — putting aside greed & distress with reference to the world. MN 10

Here, SN 54.8 states: 

If a monk should wish: 'May I — quite secluded from sensuality, secluded from unskillful qualities — enter & remain in the first
  jhana: rapture & pleasure born from seclusion, accompanied by directed
  thought & evaluation,' then he should attend carefully to this same
  concentration through mindfulness with in-&-out breathing. SN 54.8

This fastest way to jhana, namely, giving up craving, is also explained in SN 48.10, which states jhana is reached by making 'letting go' ('vossagga') the meditation object. 

There is the case where a monk, a disciple of the noble ones, making it his object to let go, attains concentration, attains singleness of
  mind. SN 48.10

Metta is not the fastest way to jhana because it is based in thinking. MN 19 states wholesome thinking is an obstacle to jhana. 

As I abided thus, diligent, ardent and resolute, a thought of non-ill will arose in me…a thought of non-cruelty arose in me. I
  understood thus: ‘This thought of non-cruelty has arisen in me. This
  does not lead to my own affliction, or to others’ affliction, or to
  the affliction of both; it aids wisdom, does not cause difficulties
  and leads to Nibbāna. If I think and ponder upon this thought even for
  a night, even for a day, even for a night and day, I see nothing to
  fear from it. But with excessive thinking and pondering I might tire
  my body and when the body is tired, the mind becomes strained and,
  when the mind is strained, it is far from concentration.’ So I
  steadied my mind internally, quieted it, brought it to singleness and
  concentrated it. Why is that? So that my mind should not be strained.
  MN 19


user295: The way to develop Jhana using Metta is found in the Saṅkhitta Dhamma Sutta.
To start with you have to do the following:

Move the mind onto the object (vitakka) - think of a person and spread love
Retain the mind on the object (vicāra) - make sure you thinking is on loving kindness and bring up the thought again and again while keeping out other distraction

Metta lead to concentration. 

One’s mind easily concentrates.

(Ekā,dasa) Mettânisaṁsā Sutta
This does not mean it is the fastest way. This depends on your temperament and past life practice. If you have been practicing another form of meditation this might give quicker results. The Buddha is only person who can tell the easiest way one can achieve Samadhi or whether one can achieve it. (E.g. Cullapanthaka's story) But nevertheless, this is one effective way to achieve concentration.
Metta meditation has 2 objectives:

develop the quality of loving kindness
break barriers where one classifies being into categories (friend or foe, same clan or unfavorable clan, etc.) which one evaluates favorably, neutral or unfavorably and reacting to it with sensations which are pleasant, neutral and unpleasant where by developing craving, ignorance or aversion.

To get into Samadhi you need to develop the Jhana factors. Suppressing the 5 Hindrances does provide conducive ground for Jhanas factors also to develop. Jhana is result of developing the Jhana factor and suppression of the respective hindrance. So the fastest way for this is the most suitable Kammaṭṭhāna to develop the Jhana factors. Since the Buddha is not there finding this is a trial and error process. Also there are some subjects which are more suitable for certain type of people. Jhana factors displace the Hindrances also, but displacing Hindrances alone does not lead to Jhana unless Jhana factor arises. As iterated before suppressing the hindrances give fertile ground for the Jhana factors to arise.
Also might be of interest: Mettā Bhāvanā Sutta, (Aṭṭha) Mettânisansa Sutta

user-1: 
I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it? 

It depends on the practitioner. All beings have different Kamma. Some have sharp and balanced faculties and others must work more diligently on theirs.
The initial effort/goal of any (Samatha)meditator must be to quiet down the five hindrances. They are an obstruction to Samatha meditation. As long as the hindrances are present strong concentration (Jhana) cannot arise.
The two most influential hindrances are 1) sense-desire and 2) ill-will. The Buddha often talked about how ones faculties cannot remain sharp if one is prone to indulge in sense-desires, e.g. in MN 75 - Magandiya Sutta:

"So too, Magandiya, in the past sensual pleasures were painful to
  touch, hot, and scorching; in the future sensual pleasures will be painful
  to touch, hot, and scorching; and now at present sensual pleasures are
  painful to touch, hot, and scorching. But these people who are not free
  from lust for sensual pleasures, who are devoured by craving for sensual
  pleasures, who burn with the fever of sensual pleasures, have faculties
  that are impaired; thus, though sensual pleasures are actually painful
  to touch, they acquire a mistaken perception of them as pleasant."

So the fastest way in any form of Samatha meditation is to ensure that the hindrances are kept in check. 
This can be done in a number of ways; most importantly is to guard/restrain the sense-doors. 
That can be done either by practicing

Morality (precepts)
Mindfulness (guarding the sense-doors, Right Mindfulness)
Attaining Wisdom (into the 3 sign of existence)
Patience and Forbearance (Khanti)
Effort (Right Effort from the Noble 8-fold Path). 

If just one of these methods arises then one has fulfilled the goal of restraint. 

How is Metta properly cultivated as a meditation?

See my in-depth and detailed answer on how to pratice Metta Meditation correctly.

As in how to develop the Vitakka Vicara on metta in meditation? 

Vitakka and Vicara is practiced in the same way as in all other forms of Samatha meditation.
Vitakka means to apply the Mind to the object and Vicara means to continually keep the Mind on the object. 
Vitakka is like striking a bell once.
Vicara is like striking a bell continually with a little pause between strikes so that the bell sounds will have a balanced and continuous flow.
Hope this helps. If you have any questions to the post feel free to ask.

10105: <p>I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it? How is Metta properly cultivated as a meditation? As in how to develop the Vitakka Vicara on metta in meditation? </p>
 -1: <p>If I were you, I'd try the slowest way to samadhi.  Generally, the more results-oriented your meditation is, the worse it's going to go.  </p>
 -1: <p><em>"<strong>I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it?</strong>"</em></p>

<p>Like @Lanka said, I think the fastest way to samadhi is the fastest way you can overcome the five hindrances, and there's a large repertoire of trainings for doing that (e.g.
 <a href="https://buddhism.stackexchange.com/a/20444/382">here</a>), including metta meditation, mindfulness of the body, meditation on unattractive, etc.</p>

<p>metta is particularly effective as a practice to overcome the presence of anger / ill will.</p>

<p><em>"<strong>How is Metta properly cultivated as a meditation?</strong>"</em></p>

<p>This is the standard description of metta training in the suttas:</p>

<blockquote>
  <p>a bhikkhu abides pervading one quarter with a mind imbued with loving-kindness, likewise the second, likewise the third, likewise the fourth; so above, below, around, and everywhere, and to all as to himself, he abides pervading the all-encompassing world with a mind imbued with loving-kindness, abundant, exalted, immeasurable, without hostility and without ill will. </p>
</blockquote>

<p>In more detail, one may use specific beings as target of the practice and increase it's range progressively until it's boundless, towards everyone. Or, alternatively, one may use some phrases such as "may all beings be free of enmity, free from affliction, at ease" (I think these are in the Paṭisambhidāmagga).</p>

<p>Or, alternatively, one can arouse a metta attitude and progressively expand it, as per the passage above, irradiating it in one direction after another, making the mind completely immersed in it, all pervading and  boundless. </p>

<hr>

<p>Personally, I let many images come to my mind and imagine myself always trying to ease the burden of others, with the desire for them to be well. At this point, I don't usually focus on anyone in particular, as I find this much harder. So these images may be memories or my own imagination -- but I just imagine to the extent that it increases metta, without getting lost on imaginations.</p>

<p>Then, there's a distinct pleasant feeling, both physical and mental, that arises from that. At that point, it's self enforcing, as it seems the mind inclines naturally towards that pleasant feeling. Then I try to expand that metta attitude until I'm completely immersed on it, as per the sutta, progressively to all directions. When I feel completely immersed on it, I abide on that all around irradiating, without focusing on any particular direction. </p>

<p>So, effectively, I expand it until I <em>become</em> a loving person towards all. In other words, until I feel it becomes my reflex to help others without hesitation, whoever it may be -- so only at this point, when metta is strong, that I try to think of particular persons who I would otherwise find myself having difficulties being good towards them.</p>
 8157: <p>'<em>Satipatthana</em>' meditation is called '<em>the direct path</em>' therefore is the fastest path to jhana. </p>

<blockquote>
  <p><em>This is the direct path for the purification of beings, for the overcoming of sorrow &amp; lamentation, for the disappearance of pain &amp;
  distress, for the attainment of the right method &amp; for the realization
  of Unbinding — in other words, the four frames of reference.... There is the case where a monk remains... ardent, clearly comprehending &amp; mindful — putting aside greed &amp; distress with reference to the world. MN 10</em></p>
</blockquote>

<p>Here, SN 54.8 states: </p>

<blockquote>
  <p><em>If a monk should wish: 'May I — quite secluded from sensuality, secluded from unskillful qualities — enter &amp; remain in the first
  jhana: rapture &amp; pleasure born from seclusion, accompanied by directed
  thought &amp; evaluation,' then he should attend carefully to this same
  concentration through mindfulness with in-&amp;-out breathing. SN 54.8</em></p>
</blockquote>

<p>This fastest way to jhana, namely, giving up craving, is also explained in SN 48.10, which states jhana is reached by making '<em>letting go</em>' ('<em>vossagga</em>') the meditation object. </p>

<blockquote>
  <p><em>There is the case where a monk, a disciple of the noble ones, making it his object to let go, attains concentration, attains singleness of
  mind. SN 48.10</em></p>
</blockquote>

<p>Metta is not the fastest way to jhana because it is based in thinking. MN 19 states wholesome thinking is an obstacle to jhana. </p>

<blockquote>
  <p><em>As I abided thus, diligent, ardent and resolute, a thought of non-ill will arose in me…a thought of non-cruelty arose in me. I
  understood thus: ‘This thought of non-cruelty has arisen in me. This
  does not lead to my own affliction, or to others’ affliction, or to
  the affliction of both; it aids wisdom, does not cause difficulties
  and leads to Nibbāna. If I think and ponder upon this thought even for
  a night, even for a day, even for a night and day, I see nothing to
  fear from it. But with excessive thinking and pondering I might tire
  my body and when the body is tired, the mind becomes strained and,
  when the mind is strained, it is far from concentration.’ So I
  steadied my mind internally, quieted it, brought it to singleness and
  concentrated it. Why is that? So that my mind should not be strained.
  MN 19</em></p>
</blockquote>
 295: <p>The way to develop Jhana using Metta is found in the <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2013/04/46.6-Sankhitta-Dhamma-S-a8.63-piya.pdf" rel="nofollow noreferrer">Saṅkhitta Dhamma Sutta</a>.</p>

<p>To start with you have to do the following:</p>

<ol>
<li>Move the mind onto the object (vitakka) - think of a person and spread love</li>
<li>Retain the mind on the object (vicāra) - make sure you thinking is on loving kindness and bring up the thought again and again while keeping out other distraction</li>
</ol>

<p>Metta lead to concentration. </p>

<blockquote>
  <p>One’s mind easily concentrates.</p>
</blockquote>

<p><a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/2.15-Ekadasa-Mettanisamsa-S-a11.16-piya.pdf" rel="nofollow noreferrer">(Ekā,dasa) Mettânisaṁsā Sutta</a></p>

<p>This does not mean it is the fastest way. This depends on your temperament and past life practice. If you have been practicing another form of meditation this might give quicker results. The Buddha is only person who can tell the easiest way one can achieve Samadhi or whether one can achieve it. (E.g. Cullapanthaka's story) But nevertheless, this is one effective way to achieve concentration.</p>

<p>Metta meditation has 2 objectives:</p>

<ol>
<li>develop the quality of loving kindness</li>
<li>break barriers where one classifies being into categories (friend or foe, same clan or unfavorable clan, etc.) which one evaluates favorably, neutral or unfavorably and reacting to it with sensations which are pleasant, neutral and unpleasant where by developing craving, ignorance or aversion.</li>
</ol>

<p>To get into Samadhi you need to develop the Jhana factors. Suppressing the 5 Hindrances does provide conducive ground for Jhanas factors also to develop. Jhana is result of developing the Jhana factor and suppression of the respective hindrance. So the fastest way for this is the most suitable <a href="https://en.wikipedia.org/wiki/Kamma%E1%B9%AD%E1%B9%ADh%C4%81na" rel="nofollow noreferrer">Kammaṭṭhāna</a> to develop the Jhana factors. Since the Buddha is not there finding this is a trial and error process. Also there are some subjects which are more suitable for certain type of people. Jhana factors displace the Hindrances also, but displacing Hindrances alone does not lead to Jhana unless Jhana factor arises. As iterated before suppressing the hindrances give fertile ground for the Jhana factors to arise.</p>

<p>Also might be of interest: <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2010/02/30.7-Metta-Bhavana-S-it1.3.7-piya.pdf" rel="nofollow noreferrer">Mettā Bhāvanā Sutta</a>, <a href="http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2010/02/30.6-Attha-Mettanisamsa-S-a8.1-piya.pdf" rel="nofollow noreferrer">(Aṭṭha) Mettânisansa Sutta</a></p>
 -1: <blockquote>
  <p>I have heard that Metta Meditation is the fastest way to a samadhi mind. How effectively fast is it? </p>
</blockquote>

<p>It depends on the practitioner. All beings have different Kamma. Some have sharp and balanced <a href="https://en.wikipedia.org/wiki/Indriya#5_spiritual_faculties" rel="noreferrer"><em>faculties</em></a> and others must work more diligently on theirs.</p>

<p>The initial effort/goal of any (Samatha)meditator must be to quiet down the <em>five hindrances</em>. They are an obstruction to Samatha meditation. As long as the hindrances are present strong concentration (Jhana) cannot arise.</p>

<p>The two most influential hindrances are 1) sense-desire and 2) ill-will. The Buddha often talked about how ones faculties cannot remain sharp if one is prone to indulge in sense-desires, e.g. in <em>MN 75 - Magandiya Sutta</em>:</p>

<blockquote>
  <p><em>"So too, Magandiya, in the past sensual pleasures were painful to
  touch, hot, and scorching; in the future sensual pleasures will be painful
  to touch, hot, and scorching; and now at present sensual pleasures are
  painful to touch, hot, and scorching. But these people who are not free
  from lust for sensual pleasures, who are devoured by craving for sensual
  pleasures, who burn with the fever of sensual pleasures, have faculties
  that are impaired; thus, though sensual pleasures are actually painful
  to touch, they acquire a mistaken perception of them as pleasant."</em></p>
</blockquote>

<p>So the fastest way in any form of Samatha meditation is to ensure that the hindrances are kept in check. </p>

<p>This can be done in a number of ways; most importantly is to guard/restrain the sense-doors. </p>

<p>That can be done either by practicing</p>

<ul>
<li><p>Morality (precepts)</p></li>
<li><p>Mindfulness (guarding the sense-doors, Right Mindfulness)</p></li>
<li><p>Attaining Wisdom (into the 3 sign of existence)</p></li>
<li><p>Patience and Forbearance (Khanti)</p></li>
<li><p>Effort (Right Effort from the Noble 8-fold Path). </p></li>
</ul>

<p>If just one of these methods arises then one has fulfilled the goal of restraint. </p>

<blockquote>
  <p>How is Metta properly cultivated as a meditation?</p>
</blockquote>

<p><a href="https://buddhism.stackexchange.com/questions/19551/i-dont-like-people/19552#19552">See my in-depth and detailed answer on how to pratice Metta Meditation correctly.</a></p>

<blockquote>
  <p>As in how to develop the Vitakka Vicara on metta in meditation? </p>
</blockquote>

<p>Vitakka and Vicara is practiced in the same way as in all other forms of Samatha meditation.</p>

<p><em>Vitakka</em> means to apply the Mind to the object and <em>Vicara</em> means to continually keep the Mind on the object. </p>

<p>Vitakka is like striking a bell once.</p>

<p>Vicara is like striking a bell continually with a little pause between strikes so that the bell sounds will have a balanced and continuous flow.</p>

<p>Hope this helps. If you have any questions to the post feel free to ask.</p>
