Your appearances is of little consequence. Try to be a bit more confident about yourself. Trust me that works.
If a girl likes you she will like you for who you are. Inside and out. Just relax. Be positive! Smile. Nobody wants to be around someone who has a negative outlook.

And how to pick the signals... Ehm, I do know that I always play with my hair when I like a guy. I heard about that bodylanguage thing. You should check for those signals. That's usually the best thing to do. Because it's really hard to fake body language.

Good luck.

__________________