I think more people should smile more. Enough people have said it enough times in enough ways. But what I mean is that more people should make it a habit to smile at a stranger. We are so full of suspicion and skepticism nowadays that we never make an effort to just smile and all it takes is a second.
I tried it today while I was riding to work. I smiled at a random person while I was stuck at an intersection waiting for the signal to change. And this person smiled back at me. It was so simple, so pure. And it left me feeling happy for the rest of that day. I know it wouldn't work all the time and that most people would probably react with puzzlement or indifference. But hey, it's a nice thing to do. And who knows you might just make someone else's day.
And I think this would work best in the mornings, when everyone is unhappy about having to go to work or angry about traffic or just generally pissed off.
Give it a shot. It doesn't hurt.