Talk about the big three if you're really stumped: School, work, mutual friends. As cliched as it sounds, you really can't go wrong by asking her these things about herself.
Equally, tell her about yourself. What school/work/interesting friends do you have? Were you a crazy kid or a quiet kid when you were young? Do you believe in Communism?
Don't run on a script. You can START by asking how her day went and include school/work/etc. in it, but just naturally branch from there.
You'll only be shy if you think you suck/aren't as kewl as she is. Just remember that she's just a chick, therefore meaning she can't possibly be as l33t as you.

WTF do you have to be afraid of?