1. Dialogue should be brief.
2. It should add to the reader’s present knowledge.
3. It should eliminate the routine exchanges of ordinary conversation.
4. It should convey a sense of spontaneity but eliminate the repetitiveness of real talk.
5. It should keep the story moving forward.
6. It should be revelatory of the speaker’s character, both directly and indirectly.
7. It should show the relationships among people.
Dialogue has to show not only something about the speaker that is its own revelation, but also maybe something about the speaker that he doesn’t know but the other character does know.
Dialogue in fiction should be reserved for the culminating moments and regarded as the spray into which the great wave of narrative breaks in curving toward the watcher on the shore.
Good writers do not litter their sentences with adverbial garbage. They do not hold up signs reading “laughter!” or applause!” The content of dialogue ought to suggest the mood.
JAMES J. KILPATRICK
Nouns, verbs, are the workhorses of language. Especially in dialogue, don’t say, “she said mincingly,” or “he said boisterously.” Just say, “he said, she said.”
JOHN P. MARQUAND
A man or woman who does not write good dialog is not a first-rate writer.
GEORGE V. HIGGINS
Dialogue that is written in dialect is very tiring to read. If you can do it brilliantly, fine. If other writers read your work and rave about your use of dialect, go for it. But be positive that you do it well, because otherwise it is a lot of work to read short stories or novels that are written in dialect. It makes our necks feel funny.
Dialogue which does not move the story along, or add to the mood of the story, or have an easily definable reason for being there at all (such as to establish important characterization), should be considered superfluous and therefore cut.
To write successful dialogue the author must have access to the mind of all his characters, but the reader must not perceive any more than he would in real life.
Don’t write stage directions. If it is not apparent what the character is trying to accomplish by saying the line, telling us how the character said it, or whether or not she moved to the couch isn’t going to aid the case. We might understand better what the character means but we aren’t particularly going to care.
Remember that you should be able to identify each character by what he or she says. Each one must sound different from the others. And they should not all sound like you.