I'd actually suggest not immediately getting involved. Take a few weeks and get a feel for how your grades are doing and what you need to improve on before joining clubs and sports.
Id also suggest studying more than you think you'll need to for the first few weeks. You'll want to know that fundamental information for later classes, and it's easier to learn it now rather than later.
Its very different from high school, in both good and bad ways. I'm sure you'll enjoy it, but if you're going to an expensive university, expect classes to be hard