What to say?

OKAY! First things first! Ready for it? *fanfare and drum roll* here it is: RELAX! If you want to know what will make you freeze up or begin blabbering incessantly (experience talking here) it is getting too wound up. Just take a deep breath when you begin to feel nervous, and let the tension run out of you.

Okay, now for the second most important thing. What to talk to him about? My advice is that you don't make a list or agenda at all. Sure, have something in the back of your mind, things generally that you always wanted to know about him, or things just in general. Don't make it sound like an interrogation, but rather make it use a conversation as you would do with your friends. Where are you hanging out? If you're going to a movie or something like that, ask about his favorite movies, and then you can talk about them. If you're going for a bite to eat, ask about what he likes to eat (the "way to a man's heart is through his stomach" and all that).

The most important things, though, is to relax and be yourself. Have fun, and I wish you the best.