1) To improve dialogue, ask what is the purpose of it.  Does the dialogue advance the story? Does dialogue carry the action? Is an important tone established? Does dialogue orient the reader? Does dialogue contribute to characterization?

2) Dialogue must not sound like actors in a stage play.  Actors have different rules.  Their speech has different rhythms and is more restricted.

3) Dialogue must be constructed with attention to rhythmic effects that should be consistent with narrative and should contribute to the reader’s process of reading the story.  Excessive short dialogue between characters may give an unwanted and deadly rhythmic effect.

4) In effective dialogue, a character’s question or idea should rarely be answered directly.

5) Modifiers used in attribution of dialogue should be tasteful.  Avoid “I love you,” he humorously chortled.