If you want to know if someone likes you they will pay attention to your conversations, the person will want to spend more time with you and the person will start to behave weirdly around your friend. Another sign is that the person will have sudden interest in your life and hobbies. Get more signs on http://www.2knowmyself.com/How_to_tell_if_someone_likes_you.
Yeah dude if a girl like's you she will want to "befriend" you. Meaning she'll want to hang out with you and talk to you, mabye get your number. She may flirt a bit to to make it clear (she'll bat her eyes, probably mess with your hair)
If she likes you she will be the first to start the conversation she will try to keep it going. She will smile at you for no reason ( even when talking.) laughing for no reason.. walking past you alot. askes for your phone # flirts/teases you/trys to make you laugh looks you in the eyes. treats you differently then others. looks & stares at you alot