Been delving into the realm of humor lately in an attempt to develope this magic wand of a skill.  The gist of what I know so far is that we should never take ourselves too seriously, stay light hearted, humble and never look like your working too hard for a laugh.  Here are a few links that I have found helpful: http://www.wikihow.com/Be-Funny
If your in Droid land there's a great informative and free text based app entitle of all things "How to be funny".  Got a lot out of that like the importance of surrounding yourself with genuinely funny people so that their wit can rub off on you.  Just be careful that they are not too funny smelling as this can also rub off on you.

Re: http://www.wikihow.com/Be-Funny

Wow this seems really complicated, wouldn't it be easier to just think about what makes us laugh and then copy that?
Best,
AR