Don't set your sights too high: We were expecting to get killed in our first tourney, and we were suprised by how well we did. It's better to be suprised than disapointed.
Also remember, although more experienced teams may know how to play fields better, paint will still break on them no matter how good they are.
If they think that a new team will be an easy max, suprise them. If they are playing sloppy, take advantage.
Oh, and have fun!