Here are some humor tips that I've mostly stolen from Scott Adams (creator of Dilbert) and Dave Barry:
The Six Elements of Humor:
Scott Adams came up with this list. The six critical elements of humor are:
Clever
Cute
Bizarre
Cruel
Naughty
Recognizable
In order for something to be funny, it must achieve two of these. Include three or more for even greater effect.
If you want to give a character a shortcut to being funny, assign them one of these attributes. For example, if you have a cute character, you're already halfway there; just show a cute character doing something bizarre or cruel, and you have all the ingredients you need. Calvin and Hobbes is a great example of this. Both Calvin and Hobbes are cute characters (Calvin because he's a precocious child, and Hobbes because he's an adorable tiger). And Hobbes is inherently bizarre (he's a talking animal). So before Watterson even tells us the joke, he's already primed us to laugh. Show Calvin being mean (cruel) to his parents or classmates, or doing something naughty, and we're hitting three or more elements out of six.
One of the biggest takeaways for me is that humor doesn't have to be clever. When I was a kid, I always observed my parents swapping parenting stories with other parents, and all of the grown-ups seemed to think that stories about childhood shenanigans were the most hilarious thing ever. Those parents found parenting stories funny because they were cute (due to their subject matter) and relatable (shared experiences of parenting). I, lacking the experience of being a parent, didn't find these stories relatable, and as a consequence they weren't funny, except when the stories involved an element of cruelty or the bizarre.
Picking inherently funny words:
Some words are just funnier than others. When you're revising a piece to make it funnier, sometimes a simple word substitution can make the passage more fun to read. Note that "funny words" are not intended to substitute for jokes; they style, not substance.
As an exercise, consider the words "pull" and "yank." Which is funnier? I think that almost unanimously, people would tell you that "yank" is funnier than "pull." So if you have the chance to substitute the word "yank" for "pull" without changing the meaning (or even better, enhancing the meaning), you should do that. You can even change the events of your story to accommodate the use of unusual words. Instead of having a character wear a green sweater, have them where a chartreuse sweater.
What makes a funny word? Generally speaking, a word is funny when it is recognizable (everyone knows the meaning), but uncommon (not often heard in everyday conversation). This is why yanking is funnier than pulling, and why a chartreuse sweater is funnier than a green sweater. Bonus points if the word has an unusual syllable that sticks out. For example, "bazooka" is a word that people are familiar with, but we don't see it very often, and the fact that it's a three-syllable word with the stress on the middle syllable makes it extra weird to pronounce. Other examples of words that are inherently funny to me include festering, girdle, regurgitate, and corpulent.
Things that almost make sense
This is one of the hardest things to pull off, and it's hardly universal, but when people like these, they love them. Sometimes, you can have a statement that just has a perfect logical break, where it
almost makes sense, but then your brain notices something is off and you have to do a double-take. Douglas Adams (Hitchhiker's Guide to the Galaxy) was great at these. For example:
The ships hung in the sky in much the same way that bricks don't.
That's an anti-metaphor. It's like a normal metaphor, but it's
just barely outside of what your brain normally expects, and it triggers a reflex in your brain that makes you laugh. Here's a feeble attempt to try and construct a "near logic" passage:
"Richard, you'll notice the copious red ink on your report. I took the liberty of marking your various errors. This should have an apostrophe since it's a contraction, this word is misspelled, and so is the one below it. And this word, it isn't misspelled, but it's pronounced wrong."
Correcting someone's pronunciation while reprimanding their report
almost makes sense, until you realize the absurdity of correcting the pronunciation of a written word.