It is only a pre-screening process. It is worthless without an in-person meeting as a follow-up (which, as mentioned, hasn't happened yet.)
I toyed around with those on-line dating services for a while back when I was single. I was moving around a lot, so my situation didn't allow for me to really get out and establish myself in one location, and in places where I didn't know anybody I figured, eh - what the heck. Let me tell you... I ended up with some wild and crazy memories and a lot I would rather forget, quickly. But then again, I wasn't looking for that special someone, I was just trying to see what the fuss was all about with those things.
So here's my advice:
a.) You don't want to come off as creepy. You must employ a great deal of patience when conversing with someone you merely met online. The women out there that are worth a damn, will carry this phase out for as long as they see fit in order to know that you are the real deal and not just some bozo looking for a cheap thrill.
b.) After a few emails back and forth it is perfectly reasonable to carry the conversation to the phone - so long as you have built up a good enough rapport with them via email. If not, refer to a.
c.) If and when a personal meeting takes place, allow her to make the call on when and where, and make sure it is a very public place, with lots of people. Inviting her over to your place is out of the question at this point. Make it as casual as possible, and make sure she understands that there are absolutely no expectations whatsoever. You're just choosing to carry on your discussion over a meal, or a cup of coffee, etc.
d.) Hopefully by this point, you have already made an impression on her. And if she is agreeing to meet you somewhere in person that speaks for itself. Don't ruin it by trying too hard for anything - let nature run its course, relax and enjoy the time you have with her.