What is the trick for writing dialogue?

That you are not running a wiretap for the FBI. I used to have a boyfriend who was an assistant District Attorney in narcotics in New York and he used to have to read wiretaps. And he would bring them home, three feet high, two women who were watching television in their separate apartments, saying, “I need Pampers! Do you have Pampers? Did you see what he just did on that show?” Four thousand pages. They were girlfriends of suspects and it was a real cautionary tale in how you don’t want people to go on and on. And dialogue is nothing at all like how people talk. Dialogue, hopefully, if you’re doing it well, is a couple of well-chosen kernels that stand in for conversation, that represent conversation. Conversation is very boring. Even interesting conversations.