How do I respond??????????????????

Ok so I was talking to this girl on myspace one day. Our conversation was going great until it all slows down and then we just "finish" the conversation saying, " yeahh" to each other. The nextthing the girl says is "soo..". And idk how to respond to that. I know someone who answers this question is going to tell me to change the subject or keep the conversation going. I think that is my problem here and I need to know HOW to do that.