Whel...I'm halfway through my college career...so here's my advice:
GO TO CLASS. period. no excuses unless you're practically dying and/or contagious. hangovers don't count as an excuse (going out the night before early class is BAD). if you *know* that 500-person lecture isn't helping you much, listen anyways or get your reading done, but go.
Talk in class...it's NOT bad to be the one person in class who raises your hand to ask a question or make an observation. The smaller and higher level your classes get, the more it will benefit you. In fact, many professors *will* grade on participation...not to mention that if you choose a large school, there are few other ways they will ever get to know who you are. And you'll need them when working out details of your major, as references, and advice (especially if you plan on going to grad school). It makes classes go a bit faster too, sometimes...and there's always the fun of 'get the professor off on a tangent for 40 minutes so we can ignore him and stop taking notes'
Do your homework/reading...it'll pay off in the end. In fact, as soon as you can, start taking electives that actually interest you...it works wonders for your GPA, no matter how difficult the course is. For that matter, don't be scared away from a class because you heard the professor is tough...just don't choose more than 2ish tough profs a semester. Some of them are the best you'll ever have.
Don't be set on your major...99% of college graduates probably aren't in the same major they picked when they started...it happens. I started with my heart set on CS/fine art double major...I'm currently a history major/complit minor and couldn't be happier (and my grades better). And don't use low GPA as an excuse to change majors...many people start off college with a lower-than-expected GPA...don't worry about it unless you're in danger of failing out...
Party safely...guys don't have to worry as much about this, but "date rape drugs" like roofies are extremely prevalent on many college campuses...get drinks for yourselves, always have yours in your hand, watch out for the friends you go with (and expect them to do the same). Rush week is a great time to go around to frats/sororities, since they're generally more open to visitors then...house parties can be great too, but don't be stupid if the cops get called and mouth off to them. And since we all know just about everyone will drink at least once in college...drink lots of water when you get back...you'll feel better later.
Respect your neighbors....especially if you're living in dorm (which I assume you will be, as freshmeat..er...freshmen). You'll probably be friends with your floormates forever, so at least be considerate enough to respect quiet hours and not need to be asked to turn music/tv/games down. By the same token, if noise is really that bad, go ahead and ask for it to be turned down...most times, people are great about it, other times, you'll have to go to your RA to get anything done..it's still worth it.
Be nice to your roommate...you'll be friends with him/her/them for a long time to come (living with someone for a year tends to do that to you). In fact, I'm still friends with Xan's sophomore year roommates, if that tells you anything... It doesn't take much, and when you do need a favor, it might actually get done....besides, it's fun having someone to pull all-nighters with, get lost with registration with, and find stuff on campus with...
Sleep...once a day is nice, more than 2 hours at a time is nice...you'll find that you do better in classes and you're less cranky with people. Losing sleep adds up, so at least take that nap in the afternoon if nothing else.
Get a job...you'll meet people, get something to put on your resume, and have a little spending money. Most jobs around campuses realize that you're a student and won't give you overwhelming hours and will be flexible around exams. (hey...I met Xan..what could be better than meeting a great s.o.? AND the resume experience is giving me the chance to be picky about summer jobs and demand actual money...)
That just made me feel REALLY old...hope you appreciate it anyways ;p
~Ladi