LadyRedditors - You're a girl whom I don't really know, but we've seen each other - I'm cute, you're cute - What do I say?

At school, I see this girl, she sees me. Smile, smile. That's all. What do I say? I've got plenty of stuff to talk about, but I can't just launch in to this or that on the spot. What's a nice thing for a girl to hear from a guy in a random situation? Help me out girls! :-)