Ha, well I'm no expert - so my opinion only. You shouldn't really hit on your visitors!
I used to help running a bar too, and it doesn't work. I think the best way for you is to invite girls from OUTSIDE of your bar, INTO your bar.. then it's fair game!
so you chat up some girl in another bar, or on the street, then you tell her.. hey - I run a bar nearby - want to have your opinion on our new dish or cocktail or something.. drop by tomorrow.. then she comes, by herself, hopefully, or may be with friends, but she comes to see you! And then you offer her something "on the house".. and you can hit on her all you like! :P well that's my opinion