Learn Your Limits
College is a transitional period between childhood and adult life. As such, it's a time for experimentation. You don't have to do any of those things mentioned in the previous paragraph, but there's also a good chance you will, even if you weren't planning to when your parents hugged and kissed you goodbye at your dormitory door. Just remember that old expression: All things in moderation. And that even older expression: Be careful out there.
There are going to be parties in your dorm. Kegs of beer are going to appear from mysterious places. It's up to you to decide whether to partake in this. (We'll assume you're of legal age to do so.) Just don't overdo it. It won't take too many keg parties before you notice that drinking too much beer in the evening leads to a lot of pain the next morning, so learn to recognize when you've had enough.
As for sex...well, that's up to you, just remember to do it safely. (Hint: Use condoms. And see your college health counselor about other forms of birth control.) And if illegal drugs show up at the party, just remind yourself that you can get arrested for using them or even for being at the same party with them. Pretty early on, decide what your limits are on all these things. Have fun partying, but just because your parents aren't around doesn't mean you can now do anything and everything you want to. Even if sometimes it feels that way.