What do I talk about when I meet this girl?

[Nick]

These guys just moved in upstairs. I live in the basement. yesterday they had a Halloween party and I was sleeping in my bed and heard all this noise which made me come out and see what was it all about. I came out and saw this girl smoking outside apart from the party. I introduced myself and asked for a smoke. While we were talking some other guys and girls came out and asked me if I wanted to join them. Well, I went in and had a couple of beers. I mostly stood by this girl and kept talking. After sometime I realized that she just came by for a good time and none of the guys in there were her boyfriend. At the end she came out to say bye and Hugged me really tight and said that she will be around every weekend. I can tell that she liked me as much as I did. Also gave me her full name so I could add her on facebook. My problem here is that what do I talk about. What if I run out of words. English is my 2nd language but I can speak it fluently with a almost no trace of accent. I have no experience in having a girlfriend before and I am almost 21. I can use some help here. So help please.