They have something in common. I ALWAYS smile and even talk with someone with dogs. It's a common interest that I know we have in common. So, on a
trail, it's the same thing. We have hiking in common.
I live in a small town and we always smile and say hi, even on the sidewalk or in a car.

I love it! If someone doesn't smile or say hi, we know
they're either new here or from out-of-town.