How to Insult Someone
If you really want to insult someone, start off by saying something positive about the person before twisting it into something demeaning. For example, try saying “I never forget a face, but in your case I'll be glad to make an exception.” Give your delivery a slight pause after your opening line to make the insult hit harder. If you're so mad and tired that you don't care about being particularly clever, dive in with name-calling and attacking their incompetence, as in “your cooking sucks”. To really hit the person hard, insult an accomplishment they put a lot of time and effort into. By making fun of their pride and joy, you'll make them sensitive about something that may have given them confidence.
Decide whether to be broad-based or specific. Your insult can either be broad, such as wearing a T-shirt with an insulting message intended for no specific person or directed to a specific person for a specific bad behavior. Broad insults are great for days when you are angry at the world or want to be seen as a crusty curmudgeon while specific insults are best when you want to haul someone up short for doing wrong by you. Being specific also lets you focus on the person's behavior instead of on the person as a whole when the person's action is what makes you deliver an insult. Being broad-based, in contrast, can be useful when you have had enough of a person because of the sum total of his or her bad behaviors and wish to have nothing further to do with that person. Here, an Old World-style curse to wander the earth forever and never know a moment's peace may be better than a few choice words from Don Rickles' repertoire. Decide whether to be direct or indirect. You can deliver your insult directly to the recipient of your wrath in no uncertain terms, damn him or her with faint praise, or let someone else insult the recipient for you. Insulting the person directly requires you to be willing to confront others, both the person you are insulting and any of his or her supporters who may be within earshot. You will also have to be prepared for any possible reprisals, whether in the form of counter-insults, threats, or acts of violence, or criminal acts against your property. Damning with faint praise means to use words that sound innocuous or even complimentary, but are actually intended to put someone down. Examples would be calling someone "alliaceous" or "cepaceous," which compare the person to a bulb of garlic or an onion, or branding someone who speaks nonsense a "phlyarologist." These words are best delivered in a gentle tone of voice and to recipients whose vocabulary is not as large as yours. Letting someone else insult the person for you can mean reporting actual derogatory comments made by a third party to the recipient, embellishing the third party's comments to make them insulting or attributing your insult to a third party when delivering it to the recipient. All these options require the third party to be someone whose opinion would matter to the recipient without the recipient's checking to verify the third party actually said what you claimed the third party did. Be aware of the culture the recipient comes from. As the world increasingly becomes a global marketplace, you are more likely to encounter people of any ethnicity and culture than before. Each culture has developed its own insults according to what it considers the most offensive things, which may or may not be the same as yours. Animal references are popular, such as the German ''Schweinhund'' (“pig dog”) or ''Esel'' (“jackass”). Scatological references (bathroom humor) are also common, such as calling someone a “p*** artist” in Ireland, meaning the person urinates on himself or herself when drunk. Other countries prefer going Number 2, as in Taiwan's ''Gou pi'' (“dog f**t”) or Bosnia's ''Sanjam da prdnem na tebe'' (“I dream of f**ting on you”). Some cultures go in for sexual references, such as China's ''Ham sep lo'' (“salty wet man”), their way of calling someone oversexed. Wishing someone harm always seems to be in style as in the Dutch ''Krijg de kanker'' (“Get the cancer”), which sounds so much cooler than the classic “Curl up and die!” Then there's the Bosnian '' A bog da ti kuca bila'' (roughly, “May your house be live on CNN”), which is equivalent to wishing your celebrity crush be stalked by paparazzi for the rest of his or her life for not giving you an autograph. Some cultural insults border on the downright funny, such as the Japanese ''Tofu no kado ni atama wo butsuke shinjimae'' (“Hit your head on a corner of tofu and die''). You might hurl this insult at your celebrity crush for not giving you an autograph if the person is a vegetarian with a reputation for either bad luck or clumsiness. A few cultures are noted for their intolerance for the foibles of others. Yiddish, notably, has words for people who brag (''barimer''), overeat (''fresser''), are cheap (''karger''), are clumsy (''klutz''), are losers (''schlemiel''), or always have bad luck (''schlemazel''). Perhaps they simply like to ''kvetch'' (whine). Sometimes, you can use the rules of a culture's etiquette to your advantage to enhance the insult. German has two words for the singular “you”: the formal “Sie” and the casual “du.” It is considered bad form to address someone as “du” before you know them well. Calling a stranger ''du Esel'' is adding insult to insult. Attack what the recipient is most sensitive about. Directly attacking the recipient by name-calling is not always necessary to insult. You can instead attack a person the recipient cares about or admires, put down or accomplishment the person is proud of or a skill the person is trying to master, mock a particular mannerism, or highlight something you find particularly annoying. People who the recipient cares about are often members of the person's immediate family. One insult of this type is the "yo momma" joke, where the insult describes how fat, lazy, ugly, old, poor, or stupid the recipient's mother is supposed to be: "Yo momma so old, her prom date was a Neanderthal." These jokes became popular in the 1990s; by the mid-2000s, MTV had built a series around them. Skills that are often targeted for insults include driving or cooking, as in "You treat me like a god. Everything you make is either a burnt offering or a sacrifice." Similarly, the most effective insults targeting the recipient's mannerisms are for those mannerisms the recipient is most self-conscious about or those he or she knows bother you most and are often delivered by exaggeratedly copying those mannerisms. Insulting the recipient's accomplishments can be particularly biting if the recipient has put in a lot of time and effort into them. Imagine how S.J. Perelman felt after the publication of his first book "Dawn Ginsbergh's Revenge" when Groucho Marx told him: "From the moment I picked your book up until I laid it down, I was convulsed with laughter. Someday, I intend reading it." Start with an apology to soften the blow. If you think the recipient is likely to take what you say the wrong way, you should soften your words by leading with something that sounds like an apology, such as "with all due respect" or "I'm not saying this to make you angry." The danger with this approach is that your intended apology will probably not be seen as sincere once the recipient hears the insulting part of it, and claiming you are not trying to make the person mad may actually anger him or her. Start with an innocuous opening, then twist the knife. With this style of insult, you start off by saying something that sounds either neutral or positive, and then turn it into something demeaning to the recipient. This style is often used by comedians in their nightclub routines. Groucho Marx was a master of this style of insult, with lines such as "I never forget a face, but in your case, I'll be glad to make an exception" and "I've had a perfectly wonderful evening, but this wasn't it." If you decide to use this style of insult, pause shortly after your opening before you deliver your insulting follow-up, unless your insult is short, such as “I worship the ground that awaits you.” Get it out there and over with. Sometimes, you're just too mad or too tired to preface your insult with either a pseudo-apology or an innocuous opening. In that case, just hit the recipient with your insult. Ad hominem insults, or insults against the recipient as a person, are commonly delivered this way. They normally feature name-calling (“You idiot!”), but may also feature profanity or curt instructions as to where the recipient can go. Acts of incompetence can also be insulted this way, as in "Your cooking stinks." This style works particularly well with made-up insult words, such as comedian Don Rickles' famous "hockey puck." (Rickles' insults are delivered in an exaggerated "in-your-face" style that earned him the nickname "Merchant of Venom.") 
Decide whether to be broad-based or specific. Decide whether to be direct or indirect. Be aware of the culture the recipient comes from. Attack what the recipient is most sensitive about. Start with an apology to soften the blow. Start with an innocuous opening, then twist the knife. Get it out there and over with. 