Hold the door open for folks. Always for women. Perhaps they don't thank you for the kind gesture. Follow up behind them after holding said door and with an unnecessary amount of enthusiasm say 'Oh, you're welcome!'. I promise that their reaction to this is far more satisfying than the warm fuzzy feeling you get from doing a simple good deed. And now they're walking away to the rest of their day feeling like a piece of shit for not simply saying 'thank you'. It's two words. Next time, they'll know better and YOU just killed two birds with one stone. Go celebrate by enjoying a Werther's.