Be humble and coachable. The worst is when girls come into high school tryouts with the "I'm way better than anyone here! I've done allstars for _____ years/ I have ______tumbling, etc." attitude or the "I already know everything" complex. No matter how skilled an athlete is, if they think they run the show, have a negative attitude and won't listen to the coach, then there is no potential to learn/grow further from being on the team and the kid will not be picked. That doesn't mean going in to tryouts without being confident, but it just means don't go in the first day acting like you own the place and showing off. If you follow directions, work hard, and are genuinely enthusiastic/positive/have a good attitude WHETHER IN THE PRESENCE OF THE COACH OR NOT, you will do great. (They are always watching, even when you may think they are not! ;)