How do I ask out this girl I met at a store when she works there?

Let me start off by saying that I know it is in bad taste to ask someone out when they're working. Particularly because they're not there to get hit on or asked out, they have nowhere to go and it could get uncomfortable.

That being said, the past few times I have been at my local GameStop, I have seen this girl there that works there and she's really nice and really cute. We always chat each other up and she seems really cool, the last time I was in there she told me she thought my shirt was cute (a sleeping Snorlax from Pokemon). I want to ask her name and talk to her more, but I don't want to do it the wrong way.

Particularly given where she works, I'm sure a bunch of dudes come in there and try to ask her out often and I don't want to be one of those guys. I also want to respect her and her comfort level, but is there a way I can ask her out in a non-creepy or confrontational way? My best friend is encouraging me to do so by asking her what types of games she plays, ask her name and then ask if I could buy her a coffee. Advice she said has worked before when she gave it to someone in a similar position and it worked.

What do I do?