I started college some time after high-school, so I didn't just jump into it. The best I can suggest from my own experience is this...
Remember that at college, you are paying for your education, or someone is paying for your education on your behalf, whether it be a parent, a scholarship, or a grant. The best suggestion I can offer is not to wast eit. There is a whole, massive world of knowledge that you can discover in college, and it doesn't pay to waste any of it. Try your hardest. Use the resources at your fingertips. Get to know and like and be liked by your teachers. Discuss things with them, ask them questions, and show that you are an interesting person who is interested in his studies, and therefore, sets an example for other students in the process. Use college as the positive learning experience that it is, and embrace it, because if you do it right, how well you do for the next four years is going to stay with you for the rest of your days.
Just have fun, be sensible, and you'll do fine!