I hooked two friends up a little while back. The guy was nervous and asking me what to say and do, and I was like, "Dude, just keep your mouth shut." She already thought he was cute and had actively asked about him. She's interested; don't screw it up.
The rules are just different for guys and girls. A girl can say whatever she wants (on a first date--over time, you still have to possess desirable personality traits), and if she's hot, the guy won't really care; he'll still hook up with her. But a girl . . . she can get turned off by anything. Anything! One false move, one wrong word, and she can be taken out of the mood like-*SNAP*-that! Talk at your own peril, fellas.
Now if I could only heed my own advice . . .