Reminds me of when I did the Rejection Therapy challenge[1] (the game forces you to interact with strangers and get rejected). The trick for me was to try and find context in the situation - a shared experience we could both relate to that was non personal.

For example, if it's in line at a grocery store, I'd make a joke about the trash tabloids that are set up as an impulse buy. It's a safe way to start a convo, and a lot more natural sounding.

[1] http://rejectiontherapy.com/rules/