Lifehacker has a quick, fun read here on the top ten things people wished they had known while in college. I summarize them here; the comments on the original post are worth a read.
1. Go to class.
2. Go to office hours.
3. Do internships.
4. Learn job-relevant skills.
5. Go for the free money.
6. Avoid debt.
7. It’s not what you know, it’s who you know.
8. Don’t be in a rush to get out early.
9. Get involved with a sport, club, frat, political org, ANYTHING.
10. Study abroad.