Sometimes as I am walking, I like to pick a flower, or an odd looking rock, and pass it between my fingers or from hand to hand.
Then I place the flower or rock in a place it would never think to be - because hydrangeas should not grow in thorny hedges, for propriety's sake; and rough quartz stones do not belong on the top of a fence post (for how should they get up so high in the first place?).
After I have left it there, I think of the person who will come across it, and who will know that somebody intentionally placed it there. Maybe then they will smile.