I am often astounded by the openers people use and they can be superb. I'm just running this default one these days that I'm finding really hits them straight away and they laugh their heads off due to it's paradoxicality< if that wrd hasn't been invented, I just invented it. It's apparent randomness, yet potentiality crosses over so well. So, I'll just et right in front of them, and either stop them as if one would ask for directions, and I'll say "Are you the one working here to X"(Whatever it is that they appear to be doing). For example, random supermarket example. She's browsing through the whatever and "Excuse me, are you working here to blah blah about the blah blah?" Look totally vacant as if it's a totally legitimate question and you SHALL get her attention in the best way possible.
This opener, though comedic is designed to open a girly up to a story. You obviously now have her attention, as she's got the social pressure to get out of the assumption. So, by adding in a further sort of nod of that if this is a wind up then holy crap this is mad, type of element. Such as, "Oh, I was looking for the blah blah, when I can't find anyone." Even if there's a worker walking right past you can simply say, oh yeh, I saw them, but I wanted to talk to you. Smile wide.
Luckily/unluckily for us women have been fooled into thinking they now wear trousers. Obviously they're always gonna look decent if they wear them well, so they're gonna be loving the male assuming their an authority, when they're not working there at all. It makes for a fun scenario and it's just a situational opener. In waiting rooms you can assume anything, on public transport, just make something up. "Hi, are you the girl who was speaking on the radio earlier?" She'll be totally unawares, so just make up a little story that there was a girly on the radio earlier from the blah blah location and you thought you might be her. Compliment her on her attire and tell her she has a great face for radio. Utilising the situation for maxing ridiculousness will always get a girly's attention as they completely live in a different universe to us when it comes to what goes on. Good luck then!