Quote:
Originally Posted by
MetroStyles 
Making friends has been covered above. I want to highlight how much of a good idea it is to talk to your professors and get to know them. They can be good mentors and will be useful later in life. I neglected to do this and regret it. Then again, I was generally not passionate about the classes I took, which is probably a prerequisite to speaking intelligently with a prof.
Same boat here. My University was near the top in the world for research in my field, meaning the professors were all terrible at teaching but really knew their stuff if you took the time to talk to them.
As I was more interested in chasing girls, getting wasted and going to 4-day long rave parties I never really took the time to talk to any of them and I sorely regret that.
Same with fellow students - I never spent much time with the hard working, smart, future world leader type students so don't have much of this "alumni network" thing everyone talks about (I'm sure I could still score some killer weed though, if I ever went back there

)
Build a network, build relationships, do activities/sports/whatever. A few people told me that when I was in Uni, I told them I didn't need help making friends and went back to the pub for another triple vodka.
Oh, and sleep around. A lot. It's much harder to find casual relationships (or even the time for casual relationships) once you're out of college, especially with attractive 18-20 year olds.