If you don't know a girl, but stare her down to try to get eye contact, but she just acts like you don't exist, does that mean to move on because she finds you unattractive? Or do girls just not realize a guy is eying them up?
She may not realize that you're looking at her. I know I am having trouble telling if this guy is looking at me or not. It makes it a lot easier if you just talk to her. If she still ignores you while talking to her, then she isn't interested. If she takes time to look at you and talk to you, and she smiles a lot, or jokes a lot, then she would be open to something more.