Maybe just start with asking for the time/directions, whatever.
Or go to a shop and remember to ask "how are u doing" or "hows business". Don't look for the right moment (this is odd because in a way, you do need to do it in the right moment).. Just say it. 90% will respond normally or warm.
Read my article "7 Reasons You Should Talk to Strangers", I spoke about this. I work on it myself. Check it out
here.