Choose a scene that you wish would have happened a little differently and rewrite the ending.
ie: In Chapter 10 Harris lies to Elaine Peterson about the narrator, he says: "He ain't right right. It has something to do with when he was borned. They cut the cord to fast or something and his brain didn't get into the light." I wish Harris had not lied, and ruined the new relationship that was blooming with Elaine. It would have been interesting to hear some funny stories about the narrator and Elaine. I can imagine Harris interrupting the two of them, or tricking them! That would have been better than embarrasing Gary and making him seek revenge.