When it comes to my ability to write funny scenes and characters, I largely credit my obsession with New York improv; seeing, studying and doing. Many of the rules of improv apply to humorous writing.
+ Make someone a straight wo/man. A comic character breaks the rules: they are willfully or naively doing and saying the things we find funny because they’re somehow outrageous. While an audience might enjoy a comic character, they do not fully relate to them. The straight man or woman is the voice of the audience; they are the ones saying or doing what the audience would say or do. The straight character is often the main character. It doesn’t mean they can’t be funny, it just means they ground the comic characters and help facilitate their crazy behavior. Think Annie (Kristin Wiig) in Bridesmaids, Stu (Ed Helms) in The Hangover or Evie in The Regulars.
+ Deliver on a promise. Audiences love being told something odd about someone or a situation and then see it come true. Have one character claim the neighbor is obsessed with his lawn, then later (when we've forgotten about it) have the neighbor show up with three new lawnmowers (for varying weather patterns). Once you’ve established something bizarre as true, you’ll get easy laughs by heightening: all we want from that neighbor is his obsession with his lawn to get more and more pronounced.
+ Matching is fun. One security guard who loves Taylor Swift is fun enough: two makes it really delightful. Punch up your small supporting characters by choosing an odd trait and have them do what we call “matching”. These characters support and build on each other. Neither is a straight man; they are both comic roles.
+ Get out on a laugh. In improv, we’re looking for a big laugh to edit on (ie. finish the scene and start a new one). In fiction, the same rules apply. We always want to get out early of every scene anyway, so rather than let the air go out of your fantastic scene, look at cutting around the height of hilarity with a particularly choice insight from your protagonist.