Yeahyeah, more tips on writing comedy. I hope you find them useful. The usual caveat: Your mileage may vary, so don't hung up looking for exceptions to any of these basic rules. I already know they exist, and I may even provide some exceptions. Consider this not so much iron-clad rules but a beginning with which experience will help you find additional paths.
The oft-quoted "Brevity is the soul of wit": Keep it short The longer a joke is the more likely people will just run from it; patience may be a virtue, but if your target audience has to wade through twenty sentences to get to the joke, it had better be one heck of a punchline. Mark Twain and Lewis Carrol are the obvious exceptions, but then even their set-ups were pretty funny.
Keep it simple, stupid: Keep in mind that one of the limits of illustration is that there limits to portraying motion,and this can limit some of your jokes. If a joke requires movement keep that in mind it may not work as well as you would like it to, and it may take some redoing to make it work. Slapstick will usually work, but something requiring a Busby Berkeley routine or complicated gears really takes some planning to pull off.
Obscure References: The more obscure a reference, the less likely your audience will get it. This can be fine sometimes, such as coming off a con and you want to give them a shout out, but keep in mind that in general the fewer people that know about the reference, the fewer will get the joke. This also compounded that they miss the joke even if they know the reference, unless you prime it somehow; sometimes if you are not looking for a joke it you may miss it, especially if you need to think about it.
Political/Religious Humor: Looking at some of the political cartoons recently brought home the point that this is a hard nut to crack. If you do it right, such as Daryl Cagle, then not only do both sides get it, but they both smile. If you do it badly, then you just tick people off. It's why when I see George Carlin quoted that I hopes someone is not using a quote after he was sixty or so; the guy had some brilliant things to say, but he became more cynical as he got older, and at a point it just seemed that he said stuff to tick people off. So, when you go after political or religious humor, have fun, but keep in mind that it requires a deft tough and not a sledgehammer.
Know and respect your subject: This is the hardest one, but the most important one. I love horror movies; because of that love and respect for the genre I can poke fun at the genre. BUT I recently had the misfortune to read a Twilight parody. The writer had absolutely no respect for the Twilight saga, and felt like she had never read the book or watched the movie. Suffice to say that the book was pretty solid drek. So learn the lesson, kids: Do not attempt to poke fun at a genre you do not understand and do not go near it if you have no respect for it. Note that I'm not saying you need to like it, but you do need to respect it.