I don't think that flirting necessarily makes a woman look slutty, but I do believe that it can come off the wrong way. You have to remember that you are surrounded by men. So as soon as it looks like you are flirting with all of them, you will most probably be labeled and talked about. If a man thinks that you are easy, they will try to get what they can from you and move on. But if a man is intrigued by you, but you don't overdo it, then he will have more respect for you and want to get to know you better. Also, I have a rule, where I try to keep my relationships and my work seperate. As soon as you start dating customers, and more than one of them, you are crossing the line of innocent flirting and opening up the possibilty of being labeled as easy.