I am not great at chatting to girls please help 10 points?

[OSuckerForLovex]

Before I start I want to say I am 15. Please don't say I'm too young as I am mature for my age and wouldn't do anything stupid.

Anyone there is this girl I like and we used to talk a lot on facebook. I sort of ruined it by not talking for a while which i admit was my fault. Anyway I tried to talk to her 2 weeks ago but since we both have prelims soon she was not on long. I told her I will speak to her soon. So i've decided I will talk to her after the prelims. I was wanting to know after our prelims are done what should I talk to her about should I ask her how she got on, should I ignore it? I am not confident talking to girls I think we are both shy as if she sees me in the corridor she never sees me I think this may be on purpose. She ignores me if she is with her friends or by herself. We used to get on really well last year when we had a class together but we don't share any classes this year so I don't see her often. Should I continue to speak on facebook and progress from there or should I do something different? Please help.