Review your material so well that your muscle memory takes over. This allows your body to take over in a fight-or-flight response so that you don't have to think about what you are doing. Your body will do the thinking for you if you have trained it well.
De-stress. Use techniques that eliminate stress from the body such as controlled breathing, yoga and massage. This will allow you to perform at your best.
Focus your energy into one moment at a time. Often stage fright kicks in because a performer wants to be brilliant all at once. Instead, concentrate on doing each moment of your performance right. Moment to moment, you can build a strong performance.
Instead of hyping yourself up for a performance, treat the performance as just another part of your day. This will prevent your nerves from taking over and allow you to give a better performance
Allow your nerves to spur you into your next action. Use the nerves to fuel you rather than halt you.