Can you help me out?

First of all, a little background information, I am 17 and single. About a week ago I was walking my dog when a girl ran into me (not literally). She was watching her brother play baseball and her dog started barking at mine so she came across the field with her dog to me. We talked for about an hour while the dogs played and then she left because baseball was over. I would like to start a friendship with this girl, hopefully turning into a relationship. However, I didn't really get any information from her. All I got was her name, brothers name, dogs name, where she was from and some random info. So my question is how do I go about doing this? Should I just walk my dog at the same field on the same day and hope to run into her again? I think it is a longshot of me ever talking to her again. By the odd chance that I do see her again how should I go about attempting to spark a friendship with her? Should I ask her for her phone number or her email address or Instant messaging? Thanks