Hahahah!! Spider and tappin for the win.
On the real bro, Just be nonchalant and say,
"I've been meaning to ask you for a while, but do you want to go on a date with me sometime?"
Not really asking her to be your girlfriend, but more serious than hanging out..
If yes, say something like, "Cool, how does this weekend look for you?" and make plans. 3 or 4 dates tops, then make it official (or whatever you want to call it).
If no, say something like, "Thats cool, just a thought that came up." and continue just being friends until she reconsiders your boner