Yep, there's already a lot of good advice in this thread! Keep in mind that nearly everyone else in your class feels the same way you do! Everyone is going in to something totally new with no idea what to expect. Try not to get frazzled if you get lost or something doesn't go quite as planned-you're there for the learning experience and you'll have plenty of them.
See if your campus has any clubs or groups that interest you, whether they are academic or otherwise. The start of the new school year is a great time to join up, try some new things, and meet new people. If you're living in a dorm on campus, try to prop your door open most of the first weekend (or even week). I know that sounds like silly advice but it will let your hall mates know that you are friendly and welcoming and lots of people will drop in to introduce themselves if the door is open!
If you are ever going to miss or skip a class email your professor ahead of time, especially if it's a small class. Having a good, friendly relationship with your professors can really help you through your classes! Don't be afraid to ask questions or get help if you don't understand something...just don't be that guy that holds everyone up at the end of the lecture with a bunch of philosophical what-ifs.
And finally, be able to laugh at yourself! If you end up in the wrong building, or don't know where the cafeteria is, or ask something that may seem obvious-just don't take it too seriously! I had my fair share of stupid embarrassing moments my freshman year, but they're all funny talking point between my friends and I now.