Remember to relax, breathe, and have fun. Pretend that you're only riding in front of someone you're used to riding in front of, like your instructor or a friend. Deep breaths and have confidence in yourself :).
Agree with above. ALSO, show a level BELOW where you are right now, so you can show what you have mastered, instead of what you are working on, but making mistakes in. You will feel more confident. I think the idea has gone out of style. When I was taking piano lessons--I have a minor in music--my teacher(s) ALWAYS had us do recitals with last year's piece, NOT the one where we were struggling through the hard passages. It keeps you from working against yourself. Hope this helps! =D