It's ok to feel nervous. It even happens to me!
As a general rule, it's really hard to know if a girl likes you or not. You can spend days re-living your conversations, her body language, tone of voice, and still not know if she likes you or not. It's much easier just to make it clear that you are interested in her, and invite her out two or three times.
If she goes out with you, then you hug her, hold her hand, attempt to kiss her, etc. If she doesn't ever go out with you, then find someone who will.