Well if possible I would start taking dance classes. Ballet will be helpful for technical stuff, jazz is good for turns and jumps, lyrical/modern will help with your balance, and hip hop will just be fun and will help you with becoming familiar with your body.
Stretch! The month before I started taking dance classes I was stretching everyday for 30 minutes. You will want to find a stretching routine that is right for you. Even if your school's dance team doesn't require you to be flexible it will help prevent you from hurting yourself. (you can look up more stretches online if needed)
You will also want to become physically fit. A 3 minute dance will surprisingly get your heart rate up fast. Plus if you guys do competition or have a recital you may have a quick change. This means you will have a few or no songs in between to change costumes, hair, and/or shoes. No time for rest will mean you will find it hard to preform your next dance at your best ability.
Work on your core (abs), legs, and cardio the most. Your core will help keep you balanced (which means you will be able to turn more) and give your more power behind kicks and such. The leg part is pretty obvious, you need strong legs to help you with almost every move you preform. Cardio will give you the ability to do lots of dances without feeling so winded.
Remember during tryouts/auditions if they ask you to learn a combo you will want to pay attention. The first time they show a step don't dance along with them. Pay attention to their feet, the next time they show the step preform it along with them. Remember to smile, make eye contact with the people who are judging you, and make them want to want you.
Have fun and good luck to you!!
