Never been in a snow contest, but have been in many skateboard ones...
Over the years, the best contest prepping advice I can give is this:
(1) The key to doing the best YOU
are able to, is being calm and relaxed. Tension, nervouness, etc are killers. If your laid back, and having fun, then you'll do a lot better than if your are stressed and not enjoying it.
(2) The next question then, is how to you maintain level of serenity. A buddhist monk and a heroin junkie all have their own ideas how to achive it. It is something you have to work for yourself. For me, what always worked best was getting a song I really liked stuck in my head. From there, you don't listen to the crowd, your friends, the cheers, or anything....you just zone-out and listen to the "music", and groove.