Ok, first off, clear your history and erase your screename because if she finds out you come on wtf to find out how to ask her out...its pretty much gonna be you and some "l33t" porn for a while....
I'm assuming you've laid the ground work with knowing her likes and dislikes, things that make her laugh, things that she cares about....if so Take her to the beach/lake at night...start making small talk....lead into the fact that you've been spending a lot of time together and say "I've never said this to anyone before, and I dont know whats come over me but.....you are the most beautiful/gorgeous/breath taking/enchanting woman i have EVER known, and I want some of that sweet, sweet coochie" seriously though, "......and I hope this is the right time"
Lean in for the kiss...no toungue. If she pushes you away, then it wasnt going to happen either way....if you're in, then you didnt have to ask the question anyways....much more smooth than tugging on her shirt sleeve "Ahem, Excuse me Miss, I was wondering if you would be my...*heheheheh* ummmm...Girlfriend..*hehehehe*" Its fool proof. Just make sure you compliment her the whole way there....lay out a blanket...if its cold, wrap you're jacket around her....make sure you grab her hand and maintain eye contact, if you're looking around at the ground or up in the sky, you're fucked...women love confidence, if you act all geeky, its not going to charming...its going to be a turn off. I want to hear how this went, if at all....we all know that building up the balls to do it in the first place is the biggest obstacle. good luck junior.