You could try asking someone who knows him, also if you find him watching you alot then he probably does. If you're brave enough you could go up and ask!
ok thanx, well.... we are both chicks just so ya know. I like her and she has a girl but mentioned to me once that they were having problems, i do catch her looking at me while im doing stuff around her then turning away when i look at her and sometimes blushing. Just little things like that and more that make me think that maybe she does like me, if only she didnt have a gf i would have asked.
Send her an email or text (something private) explaining the way you feel, but also stating how shy you are and that you don't want to compromise her happiness for your feelings.
Speak from the heart. If she likes you back things may happen, but if they don't, don't you worry - you will find someone who loves you for what you are when you least expect it.