1.)
Don't cling to your hometown. As great as it is that you and your high school clique are still BFF's, making new friends is ESSENTIAL to staying sane in college. You WILL need someone to lend you a dollar for coffee on the last day of finals. You WILL need someone to hang with when stress is high. You WILL need connections on campus to get a good work-study job. And hell, a lot of people meet their best lifelong friends in college. Don't waste this opportunity!
2.)
Get to know your professors as best you can. I cannot stress this enough. Sit near the front, listen, ask questions, and approach your professors during office hours to talk to them about the class. Make some small talk (even if it's just about the weather, it will help them to see you as human.) You'd be surprised how many of them will be much more receptive to: writing recommendations for you, staying after class to discuss your work, and even advising you on independent study projects. If they see that you have a genuine interest in their class, or just that you are a kind, responsible human being, they will be more likely to care about your success. (Bonus: the better you know your professors, the better you'll be able to predict their grading practices.)
3.)
No one cares how dorky you look. Depending on your school, there may be some high school cliques still in existence. But forget about them, because they hold MUCH less power here. Most people will be in the same boat as you, and will gladly commiserate on any awkwardness you may feel as a freshman. Everyone has quirks, and everyone's quirks come out when they're stressed the first year of college. Use that as a jumping-off point for friendship!!
4.)
Study early, and study hard. I don't care if you're at Harvard, Cal State Fullerton, or Podunk Community College. Do NOT underestimate your course load. Your school probably has tutors for a lot of subjects, your profs have office hours for a reason, and study groups should start forming early. Get help RIGHT AWAY if you have any questions about ANYTHING.
5.)
Have fun, but not too much. For a lot of people, college means freedom from parental rules. Yeah, that's great and all, but don't lose your mind. Your grades? They matter. Your extracurriculars? They matter. Your friends and family? They matter. I'm not totally against partying or even recreational drug use. But know when to quit and bring yourself back to reality.
6.)
Meet new guys/girls. Yeah, you and your high school bf/gf are going to be together forever. I don't mean that your relationship is doomed to fail, but let's be honest. Most high school relationships don't work out. Don't be surprised if the relationship ends, and don't be surprised if you meet some new people that would be better for you than your high school sweetheart anyway.
7.) On that note,
don't whore it up either. Sleeping with one partner after the other after the other isn't a good way to expand your horizons. It's just a good way to give yourself a bad reputation and distract yourself from forming quality friendships.
8.)
All-nighters happen. Yeah, that project is due tomorrow. No, it wasn't posted on the class website. It was in that tiny fine-print note at the bottom of the syllabus that you didn't pay any attention to. Chalk it up to an "oops" and do your best to get it done.
9.)
Don't be one of those people that blames the professor for their bad grade. Some professors suck, but the difference between an A student and an F student is taking some personal responsibility. If you got a D on the first project, find out what you did wrong and FIX IT. Don't keep making the same mistakes and complaining to your classmates about how the prof wronged you. It just makes you look incredibly petty and stupid. If you really feel like you're being graded unfairly, then take it up with the professor, and after that the department head.
I'm preaching a bit, but all this stuff is a combination of stuff I wish I had known and stuff I wish I could tell my freshmen acquaintances. I hope it helps a little, but doesn't scare you too much.
College is meant to be about learning and bettering yourself, so make the most of it!