Hi mate, just be yourself, ask her out on a friendy day out somewhere and get to know each other a bit better, just don't be shy OK!! just listen to what she is talking about, make her laugh girl's like that, you will be fine
yes I agree with mech29 - just try to be yourself as it is you as a person you want her to like, dont try to be anyone else. Do you know any of her interests - just to start chatting about, could you ask has she seen anything good at the pics lately or anything like that? what she did at Christmas hols? Any study going on for exams or anything at the mo? If you get chatting about these things then hopefully the rest will follow easily.
If she fancies you then she'll be just as nervous about talking to you - she's probably asking her mates the same question right now!
Asking her about what music she's into is always a good one... then what films she's seen lately and which ones she hasn't seen yet, but wants to see... which gives you a chance to ask her to go to see it with you...
Don't start a conversation with her if your (or her friends) are around. Wait til you can catch her on her own. If you know she already fancies you, that's 90% of the work done already!