1. Don't pull all nighters to study. You actually review what you've learned while you sleep, and you'll retain it a lot better than if you cram all night. I know students who actually go so far as to use sleep as a study tool. The added bonus, of course, is that you're better rested, too.
2. Take care of yourself when you're sick. A little known fact is that most universities have clinics on campus that offer care for little or no money, plus vaccines to keep you from getting sick in the first place. Don't have health insurance? Universities generally have an affordable plan you can buy into for the bigger problems, which is sometimes even included in the cost of the tuition.
3. Be actively involved in campus life. Participate in clubs on campus and gain leadership experience.While Greek life might be fun, I'd recommend that for resume purposes you use clubs to show your commitment and preparation for the career of your choice. If you can show that you already gained experience in your field (for example, participating in a business organization on campus) and have a leadership background as an officer, it will help you when you make the transition from school to the workforce.
4. Get to know your professors early on. Many scholarships, graduate schools, and even employers require that you have recommendations from your former professors. The problem is, classes in college are really impersonal so you'll have to put in some extra effort to do this. By the time you graduate, though, you should have at least three professors who truly know you and will be willing to write recommendation letters for you.
5. Keep up your GPA. I really can't emphasize this enough. If you don't maintain at least a 3.0 GPA, minimum, your chances of getting and keeping financial aid, moving on to graduate school, or getting hired are incredibly low. It's really easy to put studying aside when you go off to college, but I think we can agree that down the road, you need a job. And without a college degree with the additional disadvantage of student debt, if you fail out of college or barely graduate, in this market you're probably going to be struggling to find a job for a while.