Dialogue should do two things: it should sound like people talking, minus the pauses and ummms and stumbling, and it should move your story forward. A couple of carefully chosen lines between two characters are much more effective than a long conversation back and forth. Try to include the couple of lines in any conversation that are most crucial, most key. The rest is often better paraphrased. Let dialogue be like subtle arrows shot through your story. Characters come alive on the page through what they say and what they do. Dialogue and action, therefore, are your vehicles for showing readers who they are dealing with in a particular story.
The best advice for preparing to write good dialogue is just to listen to the ways people talk and to the lines that come from their mouths. Write down memorable lines loved ones or not-so-loved ones have spoken to you. You know, those lines that we can’t forget, that are etched verbatim into our minds. Use these lines in an appropriate story.
As interesting as the ways people understand each other are the ways we often misunderstand. Being able to write an exchange between two people where this lack of understanding is revealed, is a sign of a skilled writer. Are the two people in the conversation listening to each other or not? Are they wanting to hear or not? Are they coming to the conversation with opposing personal agendas, and if so, what are they and how do they drive the conversation?
Aim for truth, which is what I would say in response to most any question about writing.
