I've done pick up at work before its really not hard but there's little tricks that can make it go smoother. No issues with opening and really she should be comfortable talking to you since shopping is like a drug to women.
I used to work at a music store and would just bridge back and forth from what they were looking for and her telling me about her self. Ask a bridge question like.. "so there good on cd but have you seen them in concert" almost 90% of the time they would say 'no but I want to

' I'd then throw in a change up like... I'd take you but youd have to get on the waiting list first. 'wink' and then move back to work-personal-work. Basically its all really in the bridging.
I'm working part time at a pretty public job right now as a valet and have had pretty damn good luck to be honest. Just open with something like, lol you look like you had a great flight. They open up and me being the first breath of humor and fun that they've had in a few hours its pretty simple game.