Hi, I haven't been doing this long, but hopefully that means I can remember a lot of the advice I was given when I started :)
Always look up- if you look down that's where you're going!
Stay TIGHT at all times, you'll feel lighter to your bases and it will help you keep your balance
Hold your own weight when you're going up, don't expect your bases to do all the lifting (that I imagine you already know from basing!)
I don't know what sort of tryouts these are, but if they expect you to already know the basics then it might be worth taking a private class or two beforehand.
Can't think of anything else right now, but best of luck!