The Boyhood of Raleigh,
Sir John Everett Millais,
oil on canvas, 1870,
Tate Gallery, London.
A post following Agent Bransford's Dialogue Contest asked the question: What makes good dialogue?
The cumulative answer is that good dialogue reveals character, advances plot, expresses motivation and includes micro tension.
In other words, a dialogue scene has to work just as hard as any other scene. As one poster on the thread put it, a dialogue scene has to move the plot with the same alacrity as a fight scene.
Dialogue should be easy to read aloud -- which I interpret to mean, first and foremost, that one should be able to hear the words spoken, whether you move your lips when you read or not.
Don't overdo the bon mots -- which can come across as authorial intrusive, even if the character has a smart mouth. A conversation should not be an exclusive demonstration of an author's cleverness at repartee.
Someone mentioned sub-text, that what is not said in a scene is also an important factor to the conversation. Be aware of subtleties.
Many people prefer surrounding and supporting narrative/action to give context to speech and character interaction. No talking heads. Especially no talking heads for pages and pages. Keep a balance with other narrative elements. Dialogue scenes become tiresome if extended beyond attention span.
Emphasized also was the need to give the illusion of realistic speech without the slow boredom created by genuine reproduction. Like, you know. And it often may be effective to cut to the chase and eliminate the usual introductory conversational gambits employed in real life. Nice weather we're having.
And, of course, the use and mis-use of dialogue tags. Vary their placement to imitate natural pauses in conversation. Tags -- or their action equivalent -- need not be attached to every speech line, but are often necessary when more than two people are present and speaking.
I would suggest that tags could be repeated a few times at the beginning of a conversation whenever a new character is introduced, to assist the reader in becoming acclimatized to the character's speech patterns.
Each character's manner of speaking, their diction, indicates their background, their education, their cultural influences, even their moral values. For many writers, this individuality, these subtle distinctions of voice, proves to be the most difficult to re-create in dialogue.