Basically what's a good way to approach them? In my mind it's different than say, cashiers because most of the time, at least for me, there's no reason for me to approach them.

They're working, so I don't want to get in the way of that. And my only reason for wanting to talk to them is because I think they're attractive. Not to mention it's typically not a very conducive environment for this kind of behavior.

I've made introductions, simple "Hi, I've seen you around, I'm dbaker." But that's about as far as I've gotten.