Just have a good time. It'll take you a little while to loosen up, but once you do that, settle back into your place and start having some fun, you'll be OK. And OH what a rush it is. Once you get a taste, you'll come back for more and more. Anyway, the big thing is that if you mess up, keep going and don't look back. At the very worst, your band will have to stop and pick up where you left off, and don't worry, it happens to everybody. The last time I saw Primus Les messed up the words to Tommy the Cat so many times that they stopped trying to play it and moved on with their setlist... and he's been playing that song for eleven years.

The bottom line is that if you're having a good time you'll play better and the crowd will have a good time too. It's all a matter of getting comfortable. Yes, I realize that's a big step when you're starting out, but you'll make it.