If your coach hasn't done so already, prepare a workout plan for the summer. You'll want to be in the best physical shape when you arrive on campus. The fall practices are basically the tryouts for the spring squad.
And as mentioned, keep up on your school work. Once you fall behind it is difficult to catch up.
Be ready for long days. My son's days started at 5 am for a 5:30 am work out, classes until 2 pm, then practice from 3-6 pm (sometimes later). Then dinner and any homework. In bed by 8-9 pm (10 pm at the latest). And that was just in the fall. Once the spring schedule it starts it gets worse. Weekend home series are pretty spent at the ball field all day. They had to be at the field by 8 or 9 am for a doubleheader that began at noon - field prep, BP, then warm ups. Then 6 hours of ball (20 minute break between games), then another hour or so of clean up. Then do it again on Sunday. If traveling, you might be leaving on a Friday evening or early Saturday. Mid week travel is probably the worst. You'll no doubt miss some afternoon classes (you're still responsible for the assignments) and it will probably be late getting back to campus. You'll still be expected to be in class the next morning.
Good luck and have fun!