This document provides advice on writing effective dialogue by discussing common sins or mistakes writers make. It identifies 8 sins of writing dialogue: 1) writing how people really talk instead of using dialogue to move the story and reveal character, 2) failing to give characters individual traits in their speech, 3) using speechifying where characters give long speeches, 4) using dialect or accent through phonetic spelling, 5) using excessive bad language, 6) writing exposition in dialogue, 7) writing dialogue that is too direct and puts everything on the surface, and 8) failing to listen to real people talk to understand different speech patterns. The document provides examples to illustrate effective dialogue that reveals character and distinguishes characters.