When comedian, actor, and game show host Drew Carey was starting out he tried doing standup “as a goof” while in college and it didn’t go well. After a few failed attempts, he was glad he gave it a shot and get it out of his system.
After he dropped out of college, he joined the U.S. Marines. Carey served in the military for six years and was waiting tables in his hometown of Cleveland when a radio host he knew said he’d pay him $20 a joke. He was hoping to pick up an extra $100 a week and ended up building over his career (so far) an estimated net worth of over $100 million.
This is how Carey told Terry Gross on Fresh Air how he learned to write jokes.
Drew Carey: I went to the library and I finally got a book on how to write jokes. And from reading that book, that’s what really started me. I thought, oh wow, there’s a formula to this. I can write jokes.
Terry Gross: How did the book help you to write jokes?
Carey: There’s formulas for every kind of joke writing. There really is. The example they used in the book is you take driving and write it at the top of the page. It’s all about list-making. Then you write down everything that relates to driving: angry drivers, slow drivers, fast drivers, new cars, old cars, junk cars, car washes, red lights. You write all this stuff down and then you try to exaggerate something to make it bigger than it is. Then there’s words that sound like other words and you try to make puns up that way, and use all these different techniques to take all this little lists you’ve made—angry women drivers, angry men drivers—when you detail it down you try to exaggerate it, or minimalize it, or twist it around. And then you try to make 20 jokes and try to get one good joke out of that, and that’s how you come up with one good joke. If you’re starting out, it takes you like three hours.
P.S. He didn’t say in that interview what that book he read, but if you’ve seen it in others interviews let me know and I’ll put a link to it here. In the meantime check out Comedy Writing Secrets, The Hidden Tools of Comedy, The New Comedy Writing Step by Step, and Jerry Seinfeld’s doc Comedian.
Screenwriting from Iowa 
After googling for a long time, it looks like Drew Carey went on William Shatner’s Raw Nerve and said he learned to write by reading “How to Write Jokes (By the Numbers in 20 Funny Lessons)” by Hume R. Russ. It seems to out of print and very expensive used.