Signs that a guy likes you if he is in another grade and doesn't know you?

I have a crush on a junior and i am a freshmen. My friends always "observe" for me. and they always say that he is staring at me like this morning he kept on staring at me and then at the bball game he kept on glancing over at me and this has been going on for like a week and a half now. I have never talked to him b4 but i really want to and get to know him. Idk him that much but he is really hot and he seems really nice and so many ppl have told me he is nice. But are those some signs that he might be interested in me??? What are some signs that a guy could give off to a girl if he didn't know htat girl that well and they were in a diff grade??? and also i have a another question....can u flirt with body language??