I have a crush what do I do

There's this girl in my group for climbing (out of school) who go's to the all girls school near my all boys school and whenever I talk to her I feel fuzzy inside and blush sometimes. So what do I do? I make her laugh a lot cause I'm a bit of a clownish guy but what do I do now? Should I ask for her number or ask her on a date or what cause I don't have experience apart from year 3 (I think grade 2) so I have got no clue. I'm also trying to quit on that stuff but that's irrelevant. Help