(sorry in advance for the length.)
I do standup part time and I hope to one day make a living at it. I just got started and have only done little dinky local spots, but I've gotten some good laughs before. I actually do study comedy, and break down the great ones to see what it is that works for them, and it's really helped not only my routine but my overall wit.
-Part of being funny is just paying attention. To make someone laugh, I don't have to do much, just point out something around me, and my thoughts on it. Life is just hilarious when you think about it. That's why so many comedians only talk about their everyday lives-that's funny enough as it is. In essence, a comedian is guy that simply puts a funny take on what they see. That's really all they do, that's what they're paid for.
-Another part is being smart. For the most part, comedians are pretty smart people. Of course guys like Dennis Miller and Lewis Black are smart, but guys like Dave Chapelle, Dave Attell, Denis Leary are really bright, intelligent guys that could have succeeded in any number of careers. Even the "dumb" comics that are considered low brow-Larry the Cable Guy, Adam Corolla, Jimmy Kimmel especially-are smarter than the average person. Rodney Dangerfield is a great example of that. Don't get me wrong though-there are plenty of idiots in the field. I could start an entirely new thread on that.
-Combining the above two tips, being well read helps, and reading the newspaper from time to time is great. THERE'S some real comedy for you. Politics, sports, business-it's a gold mine, and it's completely renewable. If you ever watch the "Headlines" segment on the Tonight Show, realize that none of the clips sent in are made up. The newspaper is really just one big punchline if you look at it carefully.
-The bare bones of not just comedy, but what makes people laugh, is doing something unexpected. I think that laughter is simply how we react to something we didn't expect to happen, in the same way we sneeze when a particle of dust enters our nose. It's a reflex. It's how our brain says "I didn't see that coming." That's why no one laughs at jokes they've heard before. If you want to make someone laugh, surprise them-give them a new experience.
-To go with the above tip, you have to be willing to take a chance. It's cliche for a black guy to talk about being black, but back in the 60's and 70's, it was extremely controversial for Richard Pryor and **** Gregory to say what they said. Red Foxx, Lenny Bruce, George Carlin-they're not funny because they say offensive or lewd things, they're funny because they're challenging. They challenge how their audience thinks, how they themselves think, how society thinks. They press the buttons that few are brave enough to press. They take the risk of failing and being labeled a hack, just going for shock value. But that risk is what separates them from the rest of the pack.
-Above all, HAVE FUN. If you don't think somethings funny, no one else will. Focus on having a good time (actually, don't focus. Thinking too much prevents most fun.)
-you'd be surprised how much work can go in to a little 5 minute set, like deep dish mentioned. I have a 70 page notebook that I've filled half way with potential jokes or funny observations, and I've gotten maybe 10, 15 minutes out of it. And the rehearsal is even more extreme. I know guys that can do their routine-including the way they move, talk, where they look- blindfolded. Some guys that talk to audience members always talk to whoever is sitting in a particular seat every night.
-And yes, you have to write everything down. EVERYTHING. If i don't put something to paper within 5 minutes of thinking of it, even if it's killer material, I'm never going to remember it, and it goes to waste.
-any decent comedian comes up with his own stuff. Unfortunately, most comedians are hacks and rip off other people's stuff. It's an extremely competitive field.