When running I am usually very happy, so it's no surprise that I smile at other runners and walkers as they pass me by and say, "Good Morning". Most often I get a smile back and even a return hello. When totally depleted of energy I will muster maybe a raised peace sign and a smile, but most times I will at least acknowledge the other person. But, more and more, and most often from younger runners, I get a deadpan stare, in which case after they pass silently to my greeting, I utter (under my breath, "or not"). Over the years I have gotten over the non-response. When I first started distance running I remember it really bit at me how some would simply pass you by. Then again, I WAS running in DC and like in any city people are cautious. Who knows what a smile or a greeting might bring, right? But I'd think that one could easier judge another's danger capability by engaging in a hello. For example, a drunk man stumbled out of the wooded area the other day, he was singing wildly and seemed unable to walk a straight line. As I ran by I summoned the voice of a Marine and sternly said a "good morning". In his drunken stupor the man responds, "Good morning Ma'am". Right then I categorized him as harmless.
Over the years, I have boiled down my greeting to a combination of a nod, a peace sign and a quick closed lip smirky smile. These three seem to be respectful, not too puppy giddy, not too forward, but communicate, "Hey, we are into the same sport....oh yeah!" No matter what though, I find that a greeting is something I just naturally do and have never considered not doing. How do you greet other runners?