As a writing coach, I see some of the same mistakes made in dialogue over and over again, sometimes by the most talented writers. I believe our dialogue mistakes come from a single source—not hearing and not paying attention to the rhythm of the words our characters are speaking as we're writing. We don't hear because we don't know our characters well enough to be able to hear. And we don't pay attention because we're writing too fast to listen to them and honor who our characters are in the story we've given them.
So, the first step to take to learn to write more effective, more authentic dialogue is to slow down and listen to who our characters are in the story they want to tell. There are seven common mistakes we all make from time to time when writing dialogue, and once you're aware of your tendency to make these mistakes, you can switch direction.
The John-Marsha Syndrome
The first mistake we make as we're writing along, and some of the most seasoned writers
do this, is to have the characters use each other's names constantly every other line. I've called this mistake the John-Marsha Syndrome, after the 60's comedy routine where we listened to two characters (I think this routine started on the radio) repeat each other's names over and over, sometimes in a slow and sexy way, then accelerated, then slowed back down, etc. Okay, you would have had to have been there. It seemed funny at the time.
In your dialogue, it might sound like this:
"Harriet, do you remember that we're going out with Elvis and Elaine on Saturday night?"
"Oh, no, Clarence, not Elvis and Elaine. They're so boring."
"I know, Harriet, but we made the commitment, so we have to keep it."
"But Clarence, certainly we can think of something—"
"Harriet, that's not fair to them. They're our friends and—"
"Excuse me, Clarence, they're your friends. I've never liked them."
Harriet, Clarence, Harriet, Clarence, Harriet, Clarence. Does this kind of dialogue sound natural? This may or may not be a mistake you often make, but you might want to check out some of the dialogue you've written lately just to make sure this isn't showing up. If you're doing it, it's usually for one of two reasons: 1) you want your dialogue to sound intense or 2) you want to make sure your reader knows who's speaking.