I need advice, please!?

Okay, so there is a girl that I met a little while back at a party. We really hit it off, and I like her a lot. I am fairly certain that she likes me back. Here is problem #1: we don't go to the same school (we are high school sophomores). I barely see her. However, we have run into each other a couple of times since, so it is not a huge problem. 2 of 3 of the times I have seen her, we had friends around. As long as there were other people around, we were just fine talking. However, this last time, we were alone together, and I was excited. However, we are both a little bit shy, and (although it wasn't awkward, per se) it was pretty tense. We both did not know what to say to the other. Usually, though I am quiet, I can start conversations easily (I just can't follow through for the rest of the conversation). But my head just went blank. I couldn't think of anything to say.

What I am asking about is: what can we talk about, so I can have something pre-loaded. I don't want anything like an elaborate starter to a meaningful discussion, but I also do not want some cheesy pick-up line. I just need to have something better than "how's school goin'?".