What does it mean when a boy watches you every time you go outside by yourself?

The guy is most likely into you, or he just likes your dog.... I would try talking to him, or stopping right in front of him so he gets the chance to at least say hi. If he says he likes your dog... just go "Mmm hmm" flip your hair, and walk off, he'll get the vibe that you have been through a relationship before and know when guys do and don't like you.