Dialogue benefits from variety. A good way to maintain your reader's interest is to insert a variety of beats into your dialogue. Beats are descriptions of physical action—minor or major—that fall between lines of speech. Try the following techniques to punch up your dialogue.
How to Amp up Dialogue with Emotional Beats
Use Facial Expressions
When a character raises an eyebrow or furrows his brow, this action, or beat, interrupts the dialogue and telegraphs a change in the character's emotional state. As an exchange progresses and the emotional intensity rises—as the character's dissatisfaction grows into anger, for instance—a character might set his jaw, bite his lip or narrow his gaze. His eyes may darken, his face may redden, his nostrils may flare, and so on. These are all conventional and commonly understood signs of anger. You can read a dozen clinical texts on which facial expressions most strongly signal which emotion, or you can watch a few good dramatic films or TV shows with the sound off. It won't take you long to see how the actors use facial expressions to signal emotion.
Make Them Talk with Their Hands
Characters can point, steeple their fingers, clench their hands into fists, pound tables, hold their hands up to surrender, cross their arms in front of their chests, throw up their hands in resignation or despair (though this gesture is much overused) or twiddle their thumbs (does anyone actually do that?). In the following example from the bestselling novel Wonder Boys, notice how author Michael Chabon instills movement and tension into the dialogue simply by focusing on what college student James Leer is holding:
"It's a fake," said James Leer, holding out his hand to me, palm upward. Upon it lay a tiny silver pistol, a "ladies' model" with a pearl handle, no bigger than a deck of cards. "Hello, Professor Tripp."
"Hello, James," I said. "I didn't know what you were doing out here."
"It's my mother's," he said. "She won it in a penny arcade in Baltimore, in one of those machines with the claw. When she was in Catholic school. It used to shoot these little paper caps, but you can't find the right kind anymore."
"Why do you carry it around?" I said, reaching for it.
"I don't know." His fingers closed around the little gun and he slipped it back into the pocket of his overcoat. "I found it in a drawer at home and I just started carrying it around. For good luck, I guess."
Your characters can cross the room or push back from a desk or table to get physical and emotional distance from a heated conversation, an intimate moment, or even another character. They can move in closer to become more threatening or more intimate, or to drive a point home. If a character puts a piece of furniture or some other object between himself and someone else, that's a clear signal that he's blocking the other character—emotionally, physically, or intellectually, depending upon the nature of your scene. Use movement to support and enhance your dialogue, and your readers will pick up on all this and more.
It's not hard to spot the building hostility in this exchange from Khaled Hosseini's novel The Kite Runner.
"Amir agha and I are friends," Hassan said. He looked flushed.
"Friends?" Assef said, laughing. "You pathetic fool! Someday you'll wake up from your little fantasy and learn just how good of a friend he is. Now, bas! Enough of this. Give us that kite."
Hassan stooped and picked up a rock.
Assef flinched. He began to take a step back, stopped. "Last chance, Hazara."
Hassan's answer was to cock the arm that held the rock.
"Whatever you wish." Assef unbuttoned his winter coat, took it off, folded it slowly and deliberately. He placed it against the wall.
Don't Forget the Big Stuff
If it's within your character's personality, don't be afraid to have him take big actions—throw a fit, throw a plate or throw a punch. And don't hesitate to skip the buildup if a character's personality demands it. If your character has a hair-trigger temper, bypass any eyebrow-raising and go straight to breaking the furniture.
Make sure the actions you choose are consistent with your character's traits. Every action should be a reflection of the character's objectives and emotions, and of the scene. If your character seldom shows emotion, focus on small details that show his true feelings leaking out: a tightening around his eyes, a deliberate forcefulness in each step as he walks across the room, a tense grip on a pen.
Beats like these make it easier for your reader to see and feel the emotion in your dialogue. Render your characters' words with care—and then do everything you can to make them shine.