Riding a roller coaster to the top of a hill is the set up. The pay off is the ride down the steep incline on the other side. When an earlier scene sets up something, a future scene must pay off that set up.
To be most effective, the set up in the earlier scene often appears trivial or unimportant. Then the set up’s true significance only becomes clear when the pay off occurs later on. For example in “The Shawshank Redemption,” the warden (the villain) questions the hero when he spots the hero holding a Bible. The hero completes a Biblical phrase that the villain asked him about, so now the villain seems satisfied that the hero really does read the Bible. As the villain walks away, he realizes he’s still holding the hero’s Bible so he turns around and gives it back to him.
This trivial event seems meaningless at first, until the end when the hero reveals that he dug a tunnel through the prison wall and that used a tiny rock hammer that he kept hidden in his Bible. Suddenly this revelation (pay off) makes the earlier scene where the warden almost walked off with the hero’s Bible more significant.
By itself, revealing that the hero hid a hammer in a Bible means little, but when we remember the earlier set up where the warden almost took the hero’s Bible by mistake, that makes both the set up and the pay off scenes far more emotionally satisfying.
In “Little Miss Sunshine,” the little girl’s grandfather not only uses drugs, but also enjoys looking at pornography as well. The grandfather’s odd habits grab our attention right away because of their inappropriateness, but they seem fairly unimportant to the rest of the story.
However later on, a policeman stops the family and wants to look in the back seat of their van where the grandfather’s dead body is hidden. When the father reluctantly opens the trunk, the grandfather’s pornographic magazines fall out and it turns out the policeman is a huge fan of pornography. Now the policeman mistakenly thinks the father didn’t want him to search the trunk because he didn’t want his wife to know he had those pornographic magazines hidden in back.
The grandfather’s bizarre habits pay off a second time when it’s time for the little girl to do her talent portion of the beauty pageant. That’s when the little girl says she’s going to do a dance that her grandfather taught her, and it turns out to be a strip tease.
Plant set ups in as many scenes as possible. Then pay them off later. As long as the pay offs make sense within your story, the combination of set ups and pay offs will create an emotionally satisfying and memorable story.