Follow up to DB: And don’t skip class so frequently that you might miss a date change for turning assignment in.
Shrugs People do college different ways, and experience it differently. There is no RIGHT way. And everybody telling you’ve missed out by not doing X can be ignored. 
THAT said… What I did in undergrad is different than what I did in vet school that what I’m doing now in grad school (yea, 8 years and counting in college, shut up). I am, believe it or not, much more social, outgoing, and daring now that I’m older. Heck, the “don’t come back home until sometime the next morning” didn’t start until halfway through vet school, and it wasn’t animal emergencies. 
What I want to kick my undergrad self… It is not “You didn’t do X”, but “you didn’t try X”. Fairly low key, after all. Should’ve taken more care of myself, discover that the gym is not such a horrible place, done capoeira when I wanted it then. Instead, now I’m doing the stuff I wanted to do in undergrad but was too afraid/shy to do.
What you try hasn’t to be in, popular, easy, whatever. Try a leisure course offered by the university (if there is). You want to see some foreign film being offered? Why not? Check out sports you may like (there is more than football). Check out the restaurants. See if you’re interested in travellin abroad. Try out what you want.
I like leander’s post, minus [serious mode] drunk and sex. I like an occasional beer, and I have a low threshold, therefore I don’t drink much. Going to places or hanguing around with people where that’s all they do… sucks. I don’t mean talking and drinking or listening to music or dancing. I mean just drinking, little talk. Or ALWAYS going out to drink (instead of theater, movies, shopping, food, music, dance, sightseeing). The sex part is because tastes vary, and while I like sex very much, I’ve come to the conclusion I prefer quality to quantity.
Both would be awesome, but that may be difficult to achieve, depending on where you are. In alcohol and sex, trust yourself, hear no others.[/serious mode]