I think this girl likes me but I don't know how to approach her or what to say. Help me!!!?

So, there's this girl. I think she likes me, but being the shy type I don't know how to approach her. I also don't want this to blow up in my face if, you know, I happened to have misread the situation. So, what should I do? How do I play this without like being totally embarred if it turns out that she isn't as into me as I think. I know, like impossible, right? Still I'd like to prepared for all contingencies.