Ok, I need some help with this one...
There's this girl that works in this store, red headed and incredibly cute... :eek:

I'm not an overly confident guy, I mean I like to talk to people but when it comes to making conversation I suck big time. I sooo badly want to go up to her and ask her out, but every time I see her its like my balls shrivel up, and my mind goes blank. I've never had much trouble with girls WHEN they start talking/conversating first, like if they come up to me in a bar or something but I can't go up to them and start speaking to them because I just don't have a clue on what to say, so I guess this is kind off a question for the girls. What should I say?! And how should should I approch her without looking like a muppet? Oh and her co-workers are kind of hot too, so that makes the situation even harder because I don't want to look like a fool in front of them as well... :D

Be confident, say Hi and introduce yourself. There is your starting point. Compliment her.

"You look familiar. Are you from around here?"

I'd approach her when the co-workers are busy elsewhere. Tell her you'd like to get to know her better. Tell her that the environment she's in, working, makes it hard to talk to her. Find something that you both like to do and do it. Talking about a common interest will break the ice. And, girls like to be understood. For understanding to occur, she has to tell you stuff. Ask questions, show her how much you enjoy listening to what she has to say.

Don't wait too long, or you'll find out that the time you spent going there to work up your courage only gave time for someone else to catch her eye since you never tried.