My word of advice would be to just be confident and be yourself.  You need to be confident, but don't scare here away.  Give her a few compliments, and just treat her nicely.  Don't use those corny pick-up lines you read on the internet... you'll feel like an idiot.  Don't move too fast, move slowly, and if you see that she may like you too, then maybe move a little faster.  Just be confident and be yourself, and don't pretend to be something that you're not.  If you take it slow in the beginning, it'll work out a lot better for the friendship if she doesn't like you like that.  If you move too fast, it'll destroy the friendship.