funny you should say that, I've been fooling w/ the idea of giving some stand-up a chance at a local comedy club . . . I have
some material, but I think I, too would get stage fright . . .
the main thing w/ comedy is knowing where you're going to (try) and perform . . . you have to work the crowd . . . so know about your location . . . practice in front of friends or family, and have them be HONEST . . . really, you'll know if it's funny if you can get a genuine laugh . . .
this may be some moot advice, but I like to sing karaoke, so that's really helped me build a 'stage' presence, by feeling people out in the crowd before I sing . . . I'll try to add something funny between songs, and just being in front of people w/ a mic (while performing to some degree) will help your stage fright . . .