This is a pretty commonly known task. You do something nice for someone and tell them to pass it forward, this creating a chain of goodwill and love. It's a little easier to do tangible things, like take a box of cookies (like from the store so people can read the ingredients label) and hide it in a library, with a note telling a stranger that it's your gift to them, and for them to give another random stranger a gift. Or just a compliment. Your options are limitless!

~Paint_splatt