I've been thinking about this, and in my college days, drinking, drugs, sex and that sort of thing wasn't much of a problem at all. My Christian friends weren't into that and I made it clear with everyone who was that I wasn't going to do that kind of stuff, so the people I hung out with didn't pressure me to do it with them (and if they did, the friendships didn't really tend to be all that strong or lasting). I even made a list of the major ways that I avoided those temptations: church events, Bible studies, college ministries, mission trips, hanging out at the coffee house, going to IHOP/Denny's, seeing a movie, going to the mall, going on a walk, playing sports, studying
, working, reading the Bible and many more.
However, the big temptation that I hit in college was anti-Christian worldviews. Studying psychology at a large state university, I learned the non-Christian side of things very quickly. I think it's quite important to have a support system going when you are in college, including people with whom you can openly and honestly discuss things, including struggles with Christianity. I didn't find a place where I could feel free to discuss the things I was doubting and how this affected my Christian walk until well into my last year of college, and by then I was convinced that there might or might not be any "higher power." (Since then, I've been well convinced that God exists.) I can't stress enough how much it helped me in my Christian walk to recognize that I was struggling and to have the freedom to express all sorts of ideas in a Christian environment.
Study hard and have some good, clean fun!