Be prepared to ward off peer pressure. There is always somebody who's ready to party regardless of what night it is and what you have to do the next day. You've got plenty of time to party. Besides, hangovers and class make a poor combination. Don't fall in love with the first cute person you see.
College is full of romantic opportunities.
Get to know your professors and, more importantly, let them get to know you. This can only help you when grades are tallied. Besides, some of the best friends I've made in college were professors. Enjoy yourself, but understand why you're there. By organizing your time efficiently, you'll create your optimal amount of fun time without completely sacrificing your grades.