Good luck! The only thing I can think of off the top of my head is to try not to focus too much on the audience. That can only add more pressure which you really don't need right now. I also agree with Omni that, if you mess up, just keep playing and don't look back. The mistake becomes far more noticeable when you try to go back and correct it, or if it really shows on your face. All in all, just relax and do your best-- no one can ask for anything more than that!