What to say to the girl I like? How will she react? Pls read?

Alright so last year, my freshman year of high school I met a girl in my math cl to make this quick, we really clicked became work partners and we really liked eachother. However, I was to shy to tell her my true feelings. Now during sopre year she is in one of my cles but we never really talk much. Now today I was walking with one of her close friends when she came up and started talking to her friend. Afterwards I started talking to her and I felt the sparks fly. I was asking her how her midterm went but we didn't have much time to talk as we were in different room. I ended our conversation saying I'll talk to you later and now tmrw we have a midterm together and I was wondering how I should follow up what to say etc. Also should I ask her if she wants to get lunch after or is it to soon or awkward? How will she react?