I ordered coffee the other day at a local café, and when it came time to pay, the guy behind the counter waved his hand and said, 'No, it's on the house because you have such a nice smile.'

I walked for blocks with that very smile on my face, an even larger one probably, because of that small nicety. I laughed a bit as I replayed it in my head – I'd been standing next to a drop-dead gorgeous blond who filled out her sweater very well, yet I was the one with the free coffee. A definite spring was in my step, and it was like a fresh breeze had gone through my work-clogged brain and made everything sunshine-y and nice.

And I suddenly realised how easy it is to make someone feel good, to surprise someone by putting an unexpected smile on their face.

The next day, I saw a woman on the Tube who had great style - she had put together a top to toe look clearly her own, and she radiated confidence. 'You have a fabulous style!' I blurted out, and she turned and smiled broadly. 'Really? That's so sweet – thank you! I felt a little out of sorts today actually, but that makes me feel quite better!' I hate to say it, but I felt sort of smug knowing I'd brightened her day a little – the unexpected return was I felt happy, too.

Since then I've made a promise to do it every day. Share a bit of sun, say the nice thing that's popped into your head instead of keeping it quiet just because you're a stranger. Who cares if you're talking to strangers on the street? The world will suddenly seem smaller, friendlier and more pleasant to both of you. What the hell – give it a try!

Just do it: Pay someone a compliment, smile at a stranger or two on the street, let someone have your seat on the Tube, buy a friend lunch, call your Mom just to say how much you appreciate her, buy a pretty flower and give it to a total stranger who looks like they're having a tough day – passing along a tiny bit of good will reverberates long after the good deed is done.