what should i do in this situation with a girl?

[john]

ok, so i wouldn't really call it a situation, more of a potential future situation

so theres this girl that I've known since the end of summer. Ever since we met, we have talked a lot. I got her number pretty quickly and we text/talk on Facebook a lot. We have never hung out 1 on 1, but have in groups/been at parties. I like her, and have a little assumption that she likes me back but am not 100% sure and don't want to screw it up.

Example: last night we were at a party, and i caught her looking at me when i walked in, and she approached me before i approached her. When we talk, she always makes eye contact and smiles. I guess she does some flirty things, like she was playing with my hoodie strings last night. I have literally ZERO experience with getting girls, so i don't really know what to do, as opposed to people who have been in the situation before. What should I do? I want to try to take it a step up but also don't want to screw it up...