What, so she can say "I can tell you are"?
for me, I don't treat them any differently than I would if they were my friend. So when I like a girl and am attracted to her, that's enough for me to want to know more about her. I invite her out and don't push for the specifics. For me holding onto someone isn't so important as the experience, so simply approaching it that way will either have her joining you or you going on without them. Knowing she's single means that the obvious next thing would be for you two to hang out which means she has to think about it and wonder about it as opposed to approaching it like meeting a new friend. Only its a chick we're talking about and there's things we'd do that we wouldn't do with other friends, unless they too were chicks lol.
I mean seriously, how else are we supposed to get to know someone?