One cannot help but applaud the excellent suggestion. If you want to get better at small talk (especially with a stranger) you should open the conversation by referring to something that the two of you have in common, an objective fact or an experience you are sharing.
As it happens, I have made precisely the same suggestion. See, for example, my book The Last Psychoanalyst.
Now, however, social psychologists have come up with a way to test the idea experimentally. They have discovered that I was right all along.
New York Magazine reports:
But even with all that, knowing what to say to someone you don’t know is hard. You could rely on the weather, you could try to not sound creepy saying something about their clothes. Or, as Kio Stark, author of “When Strangers Meet: How People You Don’t Know Can Transform You,” recently told The Atlantic’s James Hamblin, you could “triangulate.” You draw a conversational polygon between you, a stranger, and some third thing that you’re both experiencing. The benefits are obvious, namely that you come off less threatening or creepy than commenting directly on your prospective conversational partner, and it’s less boring than saying something about the weather.
“There’s you, there’s a stranger, there’s some third thing that you both might see and comment on, like a piece of public art or somebody preaching in the street or somebody wearing funny clothes,” Stark said in a TED Talk. “Give it a try. Make a comment about that third thing, and see if starts a conversation.”
I am not convinced that you need the image from geometry to understand the concept. If I may take exception to one point, talking about the weather qualifies well, assuming that you can say something that is not boring.
I agree totally that you should not make comments about the other person’s appearance. It is intrusive and assumes a connection that does not exist and that had not yet been built. As it happens, certain behavioral economists have recommended that when you have a first date with someone you should ask obnoxious, intrusive and disrespectful questions—like, how many STDs do you have or have you ever had an abortion?
Given that such advice has been offered up on supposedly serious authority one cheers the new book that advises you to open a conversation with a stranger by observing decorum, respecting propriety and looking for common ground.