Humor writing is the hardest form of writing there is. So don't lose heart if it doesn't fall into place immediately. It can be learned but sometimes you have to work a little harder at it. And feel free to sling any questions at me you like, I'm almost always available--just don't tell the wife that.
I wouldn't like to say I've totally mastered the comic side of writing, let's just say I've been writing humor for thirty years, and upset enough people, dodged enough lynch mobs and bribed enough executioners to have a good idea when it doesn't work. So I'll answer your questions the best that I can.