Great advice AJ, now for my 2 Pence (yes I'm in England!)...
About 2 hours before going out, do about 30 mins of exercise to burn off any nervous energy, I found this works really well. I'm not talking about weight training or anything - just a jog or a bike ride. Obviously have a shower afterwards...
Chocolate is always good, something about the chemicals in it I think... just not too much though!