Ok, here's some advice for your first few weeks at school--
(1) Be friendly with your roommate (if you have one), but by no means hang out with her all the time and shut yourself off from other people. The more people you meet right away, the better. Don't get too comfortable chilling in your dorm room or you'll miss out. It's easy to meet new friends when everyone is in the same boat. It's considerably harder in a month or two when everyone is settled into groups already.
(2) That said, stay out of your dorm room as much as possible. Don't be one of those sad freshmen who's on IM to their high school friends like 5 hours a day! Don't watch too much TV either, unless you're with a big group of kids. Break out of your comfort zone and get out there and socialize.
(3) Meet your neighbors and other girls on your hall ASAP. If you don't make introductions early on, it gets awkward later. If you don't know anybody, ask these people if they want to walk to the dining hall with you for dinner. If they have class in the same building as you, you can arrange to walk together. Ask them where they're going on the weekend.
(4) Go out as much as possible in the first few weeks. Meet people. It will be the very beginning of the academic semester, and you can probably get away with a little less studying and a little more socializing.
(5) Don't let yourself get drunk on school nights! There's nothing wrong with going out on a weeknight, but save the wild stuff for later.
(6) THE BIG ONE--Since you're rushing in a few weeks, you should be aware of the fact that any girl in a sorority on your campus is going to be checking out the freshmen girls wherever they go. You're being noticed in class, in the gym, at parties... So act right. Don't get drunk and puke in public. Don't hook up with more than one guy in a particular fraternity. Don't let yourself be involved in a gross PDA with some older guy. Just be careful, because although the first few weeks technically aren't "rush," they really matter. Things you do then can affect your chances. So be polite to everyone you meet, especially older women, and be careful whose boyfriend you may be hooking up with!
(7) Try to make some male friends who are really "just friends" (at least for the time being).
Good luck at your new school! Remember to have as much fun as possible in the early weeks, and the key thing is just to be friendly and MEET PEOPLE! The first weeks really are your best chance to find a cool group of friends, after that everyone kind of already HAS their friends. So be on the ball and don't let it pass you by!
Good luck with rush, and keep us updated