Okay, a few thoughts on this, if I may. Take it or leave it.
First, chill out. I take it you havent dated too much. There really arent a whole lot of "rules"...a lot of it you're going to have to ad lib, and play by ear. Eventually, you'll do something stupid. Thats the point. So will she.
Your first step, is to actually call that number, and set up a date. If you dont know the person really well, I've found that group dates are pretty good icebreakers. Just make sure the othet guy isnt better looking than you
There are all sorts of nice places to go on dates where you live. I'd take my girlfriend to the reflecting pool sometimes in the mall (or the waterfront), Dupont Circle, Adam's Morgan (live music!), the national Mall, etc. Pick up a copy of that free city newspaper (I forget what its called), find something in there that you might like, and go. Maybe hit a COSI or a Coldstones or something for a snack. Avoid movies on the first date, since they dont offer time to converse.
Then just go with it. A light kiss goodnight is usually safe, even on first dates I think, but you have to use your own instincts, because every girl, and every situation, is different.
Whats most important though, is your attitude. The most important thing is not getting sex, or to first base, or what have you...its the girl. Be nice to her, for heavens sake, listen to what she's saying, etc. Let a relationship grow first, and the physical parts will happen on their own, trust me.