LGBT: Is it okay to ask someone out, even if you don't know their sexuality?

[another word for happy]

There's a girl in my school that I like. We make eye contact sometimes, but I don't really know for sure if she's into me. We've never actually talked as friends before, so I also don't know if she's les/bi or not.

I'm tired of playing staring games though, so should I just go and ask her out instead of sitting here waiting for something to happen? Or would that be rude?