Being a college student, I wish I would have been given heartfelt advice from a seasoned student before I took the plunge, besides the cliche "IT'S GOING TO BE HARD! YOU WON'T HAVE A LIFE!". So here is MY two cents, because everyone knows college students need every penny they can get. :)
1. The first semester, take as many classes you'd enjoy as possible: Your advisers are probably going to push you to get into as many core classes as possible your first semester. If you're the kind of student who can handle it & want to get them out of the way, more power to you. But if you're like me, you probably aren't quite prepared to utilize the awesome study habits needed to succeed in college. If you're like this, I strongly suggest enrolling mostly in classes that are considered "electives", or even core classes that you enjoy. Try to stay away from the classes you hate or are horrible at, at least for the first semester. (You can't avoid them forever!) Study as hard as possible, develop a system for organization & studying and stick to it in the future semesters. But don't get too comfortable, realize that you'll probably have a bigger work load in the semesters to come. I found it much easier to ease into the college experience than to dive in head-first.
2. STUDY UNTIL YOUR BRAIN HURTS!: (you've probably heard this one a million times, that's because it's TRUE.) ...especially if you had a bad track record with studying in high school. Pretty much no matter what your study level was in high school, you'll need to step it up for college. Professors (unless you have the lazier ones) don't tell you exactly what's going to be on the test anymore. The test questions are spread out all over the notes, the book, and other reading materials. It's not as easy as it once was. So, if you complained about study load in High School, buckle your seat belt and call your friends & tell them you won't be able to hang out this weekend. You'll be able to have a more steady social life once you get into the swing of things.
3. Hang out with people who take school seriously: I sound like a nagging mother, I swear I'm not. If you surround yourself with people who have a drive to succeed, especially when it comes time to study for the big test or write that 596 page paper, you'll have an increased drive to get them done. This may not happen immediately, it's not like pixie dust. But you'll slowly find yourself more and more motivated to kick ass in school when you see people around you doing it. This does not mean all of your friends have to be straight A students. Just have a small circle of friends or acquaintances to boost your own motivation. (For the record, yes I'm asking you to use people for your own self-advancement. Have fun!)
4. Be strong enough in yourself to not NEED a ton of socialization: Many kids think that when they graduate high school, their social life BEGINS! This is a jaded concept. You need to go into college with enough strength in yourself to realize that missing a night out with your friends won't kill you, and it also won't kill them. If your friends hate you for not hanging out with them while they teepee yards and booze it up for one night, you need to rethink your BFFs. Try to befriend people who are also in college. People who aren't in school have a hard time understanding your desire to succeed rather than partying 24/7. Students in Japan go to school for over 300 days of the year. You have plenty of breaks and vacations in which you can socialize and party all you want. If you party more than you study, don't expect grades you can take home to mom.
5. Realize that SOMEONE is paying for your education: Whether you took out a student loan or mommy & daddy are paying for school, SOMEONE is paying for it. (I shouldn't even have to mention scholarship / grant / financial aid students. You do know that if you get bad enough grades, you lose that, right?) Sit down & take a long look at the bills you rack up for college expenses. Even if you're attending a community college, between classes, supplies, & books you accumulate a bill of around $3,000 a semester. If you're going to school for 2 years (4 semesters), that's $12,000. That's enough for a brand new pretty awesome car, or a down payment on a small house. No matter who is shelling out the dough for your education, don't take advantage of it. Keep in mind that if they're paying for it, they can just as easily NOT pay for it. Contrary to popular belief, parents don't have an obligation to pay for their children's schooling after high school. You're blessed if they did it willingly, try to let them know you appreciate it by doing as well as you possibly can.
While most of this might seem cheesy and/or cliche, keep in mind that if you've heard it a million times from a million people, it probably has some truth to it. Unless you want to work your ass off until you're 65 or flip burgers and barely scrape by on rent, you need a college education. If you can succeed without one, congratulations. You're in the minority. Don't slack off and get lazy, you'll just be in school that much longer. Get it done & over with, get an awesome job, and retire when you're 45 on a luxury yacht in the Carribean. Okay, so even people who go to college don't usually do that, but it's possible! Most of all, have fun. College is an amazing opportunity, especially if someone is paying for it for you. They're giving you something that will set you up for the rest of your life.