I was checking out at the grocery market, and I really admired the cashier's lipstick. So, I put it all out there. I said, "Is it OK if I complement you and your lipstick, or does that get me slapped across the head?" She replied, "Thank you. That really is a nice complement."
I complement random GGs a lot, and I almost always get a favorable response.
BTW, I was in full dude mode.