“One line of dialogue that rings true reveals character in a way that pages of description can’t.”
Anne Lamott, Bird by Bird
Natalie Goldberg recommends that you listen carefully to dialogue and speech when you are in public places. Yes, it’s eavesdropping. But it’s also professional development. You’re not listening to be nosy. You’re listening so that you can be a better writer. Listen carefully to cadences, slang, vocabulary and observe mannerisms, facial expressions and reaction times.
How do people reveal themselves? What are they wearing? What does disappointment look like? What about fear? Joy?
Writers are keen observers. Dialogue is part of honesty that Lamott mentioned in chapter one of Bird by Bird.
The more accurate you are about observing and recording, the more authentic your story will be.