Where I'm from, it's considered rude if you don't acknowledge someone else as you walk past them on the sidewalk. When 2 cars meet, you at least raise a finger in greeting/acknowledgement.
It took me several years to feel comfortable here on the East Coast, and over the years I have established friendships. But despite years of living in what someone once called "the small town without the warmth," I have retained my spontaneous smile. I love to go to the grocery store and cry, "Good morning!" with a big friendly smile, to which people always--always-- respond in kind. Now, granted, I am a rather perceptive person and if I sense someone is not receptive, I don't attempt the eye contact/smile. But you know what happens if you consistently greet people in a happy and friendly manner?
They do it back to you.
Maybe people are sensing my friendly demeanor before I even open my mouth now, because lately all it takes is the eye contact and guess what? THEY smile and say "good morning" or "hello" to me first!
I'm not so arrogant as to assume I singlehandedly brought warmth and friendliness to the small town that was previously lacking in it, but I do like to think I radiate affable, approachable vibes. I may have even sprinkled a few sunny little seeds around which have evidently taken root.