I can't believe I'm posting this, especially on a computer forum

but I need a bit of help with the ladies - well one in particular.
I've seen this really cute girl that works in a shop near where I work and I'd really like to ask her out but how do I go from being an occasional customer to being able to be in a position to ask her out? Or at least find out if she's seeing someone?
Just blurting it out instead of 'Pump number 7 please' would probably shock the hell out of her and scare her off at the beginning. I'm truly lame when it comes to women. I'm like Jim out of American Pie "I was born without that part of the brain."
She's got the most beautiful eyes I've ever seen (I'm a sucker for green eyes) but even saying that would be a bit odd coming out of the blue.
Any ideas guys and gals (especially gals)?
This post is so sad Im going to sit in the corner and face the wall. If you intend to post a reply tap me on the shoulder ok?