Often a humorous way of presenting an argument is more memorable, and has more lasting effect than a carefully reasoned one. Make all your jokes innocuous. Be careful that you don't joke about anything serious. If you do make a joke, direct it at what has been said, not the person who said it. This means that clever puns and wordplay are better than simple abuse of another writer.
Wit is also more difficult than insults and therefore funnier.
Mark all your humor explicitly. One common punctuation device that has been adopted by many e-mail users is the smiley face . They thought it worked well enough to be worth a 23-page journal article. Good e-mail and newsgroup style requires practice, preferably in an environment where it won't matter much if you make mistakes. A major purpose of this conference is to provide that environment.