How can you tell if a girl wants you to talk to her?

So I was taking my dog to the dog park and I noticed this girl who I have seen before she has had her dog at the park before and she has smiled at me. Today she happen to be walking her dog by the fence of the park and when she seen me take my dog in she brought her dog around to go in she was only there a few minutes but it was a similar leaving smiling at me as she left.

How can you tell if a girl wants you to talk to her?
Post Opinion