Don't sweat it if she hasn't already approached you, she's just as nervous as you are. 

Here ia an examole of a wrong way...

There's no recipe for the right way or wrong way to approach a girl actually, there are a lot of wrong ways, but barring any rude comments or physical contact, I think you'll be okay. 

If she's in a class, ask her if she could tell you what the professor was talking about 

Talking about class is a godd idea.

you were so bored you couldn't pay attention or get a study group together and invite her to join (safety in numbers).  Chances are, she's waiting for you to say anything to get the ball rolling. 

If she really is checking you out, maybe she'll get impatient and approach you first.  Either way, you're young and have lots of time to get comfortable talking to strangers of the opposite sex, just relax and let time be your trainer,