Write some letters. Then, go to the library and place the letters in some books, preferably ones that aren’t checked out very often. Or, place them in books at a used bookstore, preferably books that might not be purchased for a long time. The letters can be about anything, to anyone, but keep them anonymous, untraceable. First names only, or no names at all. The people who find the letters get to imagine the lives outside of the words on paper.