Choose a topic. Writing comedy sketches involves a broad range of comedy. By selecting the type, you can narrow down the type of sketch you are trying to execute. Watch past comedy sketches to get different ideas without blatantly stealing an idea to create your own.
Write a political comedy sketch. Political comedy sketches have been popular for years, especially on "Saturday Night Live." The key to writing an effective political comedy sketch is to make a caricature of the politicians you use, but do not go too over the top. Look for past interviews and speeches to find trends in the way the politicians speak, and base the writing off these trends to make your comedy funnier by being more realistic.
Write a pop-culture comedy sketch. Pop-culture parodies can be narrowed down to a number of subjects. For example, you can focus on a celebrity, TV show, movie, game show, newscast or mix them all together. Look for flaws within the characters or turn something around on them. For example, you could write a comedic spoof about the "Octo-Mom" becoming the new "Doc-Ock" and challenging Spider-Man.
Write a character-study sketch. These sketches have nothing to do with pop culture; they focus on specific comedic characters. For example, "Saturday Night Live" features a running gag about a strange Target worker. All of the comedy is based on her interactions with customers and how weird she is. Come up with a character of your own that can extend laughs for 3 to 5 minutes.
Write a product comedy sketch. These are often referred to as commercial spoofs and play off popular commercials and advertising campaigns. Write these by watching different commercials and coming up with alternative products that can deliver a hilarious message.
Write a classic comedy sketch. Classic comedy sketches vary in style, but there are some classic objectives you can focus on while you are writing. For example, a classic sketch features two people simply misunderstanding each other. You can write that one character means one thing while another is trying to convey something else, and the comedy comes from their misunderstanding. Physical comedy is also a big part of classic sketches, and a few slips or falls can add a lot of humor to your writing.