You can earn your degree and develop a better understanding of other cultures while having international adventures.
Learn a foreign language
Which may help with the above. And vice versa.
Take advantage of free stuff
OK, so it's not really free when you think about it. You're paying tuition to have access to things like a gym, tutoring services, events on campus, etc. You might as well partake and get as much out of the experience as possible. And besides the free stuff, don't forget to work your student ID for discounts where you can.
Write a novel, fast
Garrison Keillor once observed that the older you get, the fewer pats on the back you get for just doing anything. You may hear "Pretty good drawing for an 8-year-old," but that turn of phrase grows ever-rarer with advancing years. Maybe you'll hear "pretty good poem for a junior high student." But not for long after. Junior year is probably the last time you'll hear "pretty good" just for finishing your novel.
You're going to be really busy studying and/or nursing hangovers, but it's worthwhile to devote some time to helping others. Planting trees or volunteering at the soup kitchen will make you feel all warm and fuzzy inside and it looks really great on your resume. Especially when you weren't ordered to be a good guy or girl by a judge.
Your future professional life will be characterized by slacks in neutral tones and starchy collared shirts, so get some tattoos and/or piercings and show them off before you sign up for a 9-to-5 with a dress code. It's debatable whether or not a spiky purple mohawk is appropriate in the workplace, but you can most likely get away with it during undergrad. (Reminder: Tattooing spider patterns on your face, love and hate across your knuckles, or the name of this week's beloved across your neck are a wee bit more serious than "Go Tigers" across an ass cheek.)
Develop a caffeine addiction
Inevitably there will be long, lonely, all-night cram sessions followed by 8 a.m. exams and you can be sure that one loyal friend will be there to support you — caffeine.
Get yourself an internship
Muster some ambition and apply for an internship. It will probably be a lot of work for literally no money but the job experience is invaluable and you'll meet people and do things that could help you on your way to achieving whatever career goals you might have. (Hint: Do not send a cover letter like this one: "As an inspiring journalist, I would love to be able to work, learn, and corporate with the San Antonio Current. … )
Take a random class
Yes, college is about getting a degree and ultimately landing a job, but there's a crazy rumor going around that it's also meant to be a time of personal development. When your schedule allows, don't be afraid to take a class in something that interests you. Though it may seem superfluous, "Study of Harry Potter" will probably prove to be more fun and memorable than Chem102. (Unless you're already a popular culture major, in which case, go for the Chem.) As one Facebooker added on this popular piece of advice: "You'll learn to respect people with different skills."
Take a drama class if you're a business major
Continuing on the theme above, we've heard the suggestion that an acting class gives the aspiring business wizard an advantage over the drones who've focused solely on ROI and Ponzi schemes … oops, we mean cutting edge financial instruments. Remember, sincerity is the most important thing in the world. Once you can fake it, you've got it made.