Word. Just practice. Practice whenever you get a chance, do it until you start to nearly resent the piece you're performing for the audition. That'll stick the technique in your head until you've got it on autopilot, and you don't need to think about how you're performing, you're just performing it.
Wear something nice, cut your hair, have a shower and a shave. Treat it like a job interview, be professional.
I was as nervous as I' ever been going for my college audition this time last year, but it all paid off. Also, they're not looking for miracles, or even really talented players.
You're going there to learn music, they don't expect you to have it learnt already.
They just want to see an aptitude and an appetite for it.
Where're you auditioning?