1. Got involved early. Although I will never know for sure, I think that if I hadn't entered college eager and hungry to get involved right away, then I would have missed out on at least half of the opportunities that eventually came to me. Just like in the real world, opportunities in college tend to build off one another. So take advantage of the myriad of resources available to you and pursue your interests early. Join a club, become a student rep or start your own t-shirt company -- the sooner you start building your skills and testing your interests the better equipped you will be to capitalize on opportunities as they pop up.
2. Accepted every challenge. Nearly every single club I joined, job I got or responsibility I took on scared the crap out of me. I thought that I was under-qualified for everything I ever started. But it was my willingness to accept challenges and push myself outside my comfort zone that taught me the most. When you're not learning something new then you're not growing. And if you're not growing, then you're dying. It was the challenges that I almost didn't accept that taught me the most and afforded me the most opportunity.
3. Made friends with professors. Good professors hold interesting lectures and teach you something new. The best professors stay up late to guide you through your first media plan, throw the lesson plan out the window, challenge you to be a better student of life, and yes -- get you a job. Seek out the best professors. If you're just attending class and periodically raising your hand, then you're missing out on the best part of your education. Foster these relationships and they will pay dividends in the future.
4. Worked at the student agency. This is a no-brainer, assuming your school has one and if you want to be in advertising. The experience of working with real money and real clients on real campaigns is the most valuable career-prep experience you can have. I learned more applicable skills working in our student agency than I learned in all my other classes combined.
5. Had fun. As I said earlier, most of the best and most fun things I did in college had absolutely nothing to do with getting a job. However, the most important part of any of the things I did was always to have fun while doing them. If you don't enjoy what you do with your days in college, then you're missing the point. And if you're not having fun preparing for your career, then maybe it's not the career for you.