The great Irish novelist Elizabeth Bowen wrote one of the great writing essays, “Notes on Writing a Novel.” It’s particularly useful in terms of how to craft dialogue.

A few snippets:

• Dialogue Must (1) Further Plot. (2) Express Character.
• Dialogue must appear realistic without being so … In ‘real life’ everything is diluted; in the novel everything is condensed.
• Short of a small range of physical acts—a fight, murder, love-making—dialogue is the most vigorous and visible interaction of which characters in a novel are capable. Speech is what the characters do to each other.
• Characters should, on the whole, be under rather than over articulate. What they intend to say should be more evident, more striking (because of its greater inner importance to the plot) than what they arrive at saying.