How do you know if a girl likes you or not?

theres this girl i met in one of my classes and shes pretty cute. during the class we have together i think i see her looking over my way a couple times everyday through the corner of my eye. on friday when my friend was trying to borrow a compass from me from across the other room she pops up behind him(she sits behind him) and starts waving really hard at me with this really big smile on her face. i was kinda surprised i havent really seen her do that anyone else, but me. outside of class when i see her and im by mself she yells my name to get my attention. it also seems like when im really close to her she gets nervous. is she interested in me? what other things should i watch for?

Sounds like she is interested. Look out for: Her trying to make any physical contact like, poking you, playfully hitting you, etc. Also if she stares at you all the time. If she asks you questions like " Do you have a girlfriend?" or " Who do you like?" OR if she waits around for you or finds excuses to walk with you, or if she asks your friends about you. I hope I could help