It started when I was watching a TED-talk on non-verbal communication. In it the speaker talks about how when you smile(just by arranging your facial muscles into a smile, you don't even have to be happy), the brain releases certain chemicals that make you happy. Well enough about that, let's move to the opener. Here's what you do(what I did):

While walking down a street try to get eye-contact with a woman, as soon as you do this smile and don't break that eye contact. Keep it and approach her while smiling. When you can talk to her, say something like this:

"You probably noticed I was smiling there when our eyes met, and your also probably wondering why I didn't just continue walking and decided to talk to you. Well, the answer is that I heard somewhere that just by smiling, people get happy, and after I saw that video I thought; why not just make a little difference? Why not smile to people and maybe make their day a little better? So, there you have it! Don't you feel better already?"

I hope I could be of some help! :)

Sorry for bad english, it is not my native tongue.