well... i just finished my first year of uni, and when i first arrived i literally knew no one, and now i'd say i have about 10 close friends, and about 50 i can hang out with.
I think the best way to build is meeting people through new classes, which you've already started doing. But, rather than just talking to them in class, build a bit of a friendship, mayb go out for coffee or somethin. Just do something with them outside of class. After a while, they'll introduce you to their circle of friends, and you can become part of that group. So you only really have to create a good friendship with 1 person, and through them u'll be introduce to heaps of people.
Do this afew times, and you'll have a large, diverse group of friends
Oh, also, try and be an interesting person (i hope this isn't too offensive
)... go traveling, take up some cool hobbies, be active, this will make it easier for you to have conversations because you have you can talk about. Also, people like hanging out with interesting people