You're probably in your head thinking about what to say or how to move it along. Just speak your mind. If you're just not finding things to talk about with her, than you need to evaluate why you're talking to her in the first place.

Conversations with a girl of interest is always tricky. But a good trick is to let them do the talking. 1. Ask her how she is doing 2. Ask her what she did today/yesterday 3. if she mentions something like work/hobbys/other intrest ask her about that Just be carefull that your questions are not to specific dont....well NEVER question something while she is talking and or you don't know the girl very well. It is always good to talk to them in public don't try to hard while you're somewhere where your cant escape. Last rule is when you feel the conversation is going nowhere or she looses interest dont try to force the conversation. always be cool.