I really like this girl and I think she likes me too. What should I say to her?

She is new to the neighborhood. I'm not really good at conversating with women, so I need some advice. Every Tuesday, Wednesday and Friday she walks by my house, but most of the time she is with friends, so I can't really get the chance to talk to her, but sometimes when she's walking alone, I go outside acting like I'm getting the newspaper and I smile, and she smiles back, but she walks a little faster. I know she likes me because every time I smile at her she smiles back. What should I say to her the next time she is alone? I am 37 and she just turned 18. That's why I need some help on what to say to her.