Everyone talks to you when you're walking down the street with a nine foot tall Christmas tree. All of the stranger danger awkwardness disappears and is replaced by smiles, waves, and "Merry Christmas". This is the gist of what I discovered in the three blocks between purchasing the tree and my apartment.
I live in the city, don't have a car, and really wanted a tree. Rather than renting a zipcar, I enlisted my housemate to help carry it home. We could have purchased a smaller, easier to carry, tree, but where's the fun in that?
If I can generalize the moment into a single observation, one way to encourage conversation is to ground people in familiar, shared experiences while also doing something remarkable.