There is a myth that the ability to write great dialogue is a gift that can't be learned and can't be taught. You're born with it or you'll never have it.
One version of the myth goes something like this: you have to have an ear for dialogue in order to be able to reproduce realistic, believable, crisp, dialogue on the page.
Great dialogue does not come from having a good ear for dialogue. It does not come from having some innate gift or talent for writing dialogue. It comes from this: knowing your characters so well that you know what they will say and how they will say it when faced with specific people, situations or events.
Now that may seem overly simple and in a way it is - given the same character and same situation, two writers of very different abilities will create greater or lesser dialogue. The dialogue in Good Will Hunting and As Good as it Gets does not come out of every writer's laptop no matter how well that writer knows his characters. That's because there's an added component to both of these scripts and other scripts like these: genius. And genius dispenses with the rules of ordinary life and ordinary writing.
But, I firmly believe that if two writers know their characters equally well, if both writers develop those characters fully and if both writers know the other characters in a scene equally well, both sets of dialogue will be of a high quality.
Let's take some examples. One of my favorite films is Good Will Hunting. Let's take one particularly well-done bit of dialogue from that movie. It's not just any dialogue, but brilliant dialogue, so it ought to be a great test of my theory that all great dialogue comes from knowing one's characters.
Will Hunting, the main character played (and written) so brilliantly by Matt Damon, goes with his simply-structured childhood friends (including his best friend Chuckie played and co-written by Ben Affleck) to a bar near Harvard, frequented by that school's Ivy League students.
Chuckie spots a small group of pretty young women and decides he's going to hit on them. So the rough-around-the-edges Chuckie goes up to the girls and pretends to be a student. The girls, who are students, know immediately that he's full of it, but they graciously go along - besides, Chuckie's kinda cute, so what's the harm?
As Chuckie fumbles with trying to pass himself onto the targets of his affection/lust, a bona fide Harvard student comes up and arrogantly destroys Chuckie, exposing his lies and his lack of academic credentials and book-smarts. Just as it seems that Chuckie is about to show this guy the intelligence in his two fists, his friend Will steps forward with a brilliant dissertation that ends up being a verbal slaughter of the arrogant Harvard a-hole. Then he ends the dialogue with a very telling sentence: "If you want to take this outside."
Why is this dialogue so brilliant? Because Damon and Affleck knew who their characters were. Not just the main character, Will Hunting, but Affleck's character, and the character of the arrogant Harvard pissant. The writers also knew what event they wanted to occur in this scene, what events led up to this scene, and what repercussions they wanted this event to have.
So who is Will Hunting? Well, he's brilliant and a polymath. That's the point of the whole movie. He's a troubled ruffian; we see that fairly early on. We learn later that he was abused as a child.
Although we the audience don't know about the abuse suffered by Will Hunting at the time this scene in the bar takes place, the important thing is that the authors know about it, so it colors Will's reaction and his dialogue. Why? Because Will could just as easily have gently taken Chuckie by the arm and led him away from the scene, offering him a free beer, soothing his ruffled feathers and bruised ego, making a joke of it. The dialogue in that case would have been more than a bit different.
But you see, the authors knew their characters so well, that the event that did take place, the dialogue that was spoken, was in essence inevitable.
This is critically important to understand. When a specific piece of dialogue is the only dialogue that could be spoken in a given situation by a given character to a given character, then that dialogue can seem brilliant, and it doesn't have to be eloquent dialogue, as long as it's the exactly right dialogue.
"I coulda been a contender" resonates down through the decades even today and can certainly be considered brilliant dialogue for its poignancy and for the fact that it was exactly the right thing for Marlon Brando's character to say to the specific female character in the particular setting and circumstance he was in at that time.
Will, having been abused as a child, has a chip on his shoulder the size of an Oregon redwood. He has undying loyalty to his friends, especially his best friend Chuckie. He was born and brought up in "Southie," the southern section of Boston, the poor, uneducated Irish section, so he was considered to be white trash. He could have let Chuckie deck the Harvard snot, but then Chuckie would have gotten into trouble. He could have decked the Harvard snot himself, but there were the pretty girls to consider and besides a fistfight would have made him look even more like white trash in front of this Ivy League a-hole.
So Will's only or at least best response is to use the one weapon that would destroy this Harvard moron-in-sheepskin clothing: Brilliance. Knowledge. Erudition. Debating skills. And being right about subjects that the Harvard a-hole should have known about but didn't because he was educated, but not learned. Will is not educated, but he is learned, profoundly so.
What Will said was so perfect, so believable given who he is, where he is, who he is in relationship with, and whom he is saying it to, that it comes across as brilliant.
Another important aspect of that scene from "Good Will Hunting" is the fact that we not only like Will, we identify with him - the downtrodden good guy who fights back but somehow only succeeds in digging himself a deeper hole. We've all felt like that.
Why is that important? Because it matters to us what happens to Will, we hope for him to succeed. Thus in this scene Will does several things that make us feel good and triumphant and vindicated - he bests the snotty bad guy, he impresses the pretty girl, he stands up for his friends.
Could anyone write dialogue that brilliant? Maybe not, there is after all a touch of brilliance to the dialogue throughout this brilliantly written screenplay. But still, the elements that led up to that scene and that dialogue are all there for us to see and they are all based on the authors' complete, profound knowledge of who their character is.
There is another factor in writing great dialogue. It's the understanding that there are four key components to any story, whether screenplay, novel, play, or short story: characters, situations, events, and dialogue.
If you've read my book "How to Write High Structure, High Concept Movies," or attended any of my workshops, you'll know that I'm big on relationships. Well, what's important to know about these four key components is how they relate to each other in a cause-and-effect way.
Throughout a story, these four components will affect and effect and be affected and effected by each other. For example, a character creates a situation that causes him to create an event that leads him and others to be affected by that event, which leads the character to make a statement or revelation (dialogue) that itself causes a reaction (an event) that leads to yet another situation, the stakes rising, the jeopardy increasing, changes happening and leading to other changes and events and dialogue which affect characters who, well, you get the picture (no pun intended). But if you cause these four components to interact in just the right way, you will get the picture and maybe even your name in the credits of that picture.
So what role does dialogue play in this? Well, essentially dialogue is just another event (I know, that means there are only three key components to a story - so sue me, math wasn't my major in college). It's caused by characters and in turn causes other events and affects other characters. It's something that happens, that takes place in space and time, and is both a result and cause, just like an event is.
When characters speak, they are doing something, performing an act.
Great, but how does that help us improve our dialogue? Well, think of it this way: what happens when an event in a story occurs that has nothing to do with the rest of the story? It sticks out like a sore thumb. That's what happens with dialogue that has nothing to do with the rest of the story.
In other words (pun intended), you have to make your dialogue relevant to the story. More than just this, however, is that you have to be aware of the cause and effect of that dialogue just as you are aware of the cause and effect of an incident.
If a guy in your story waves his hands around in an unusual way and nothing comes of it, you're left wondering why he did that. If you find out that the reason he's waving his hands around oddly is that he's schizophrenic and thinks that he has magical powers and that with a wave of his hand he can make his enemy disappear or make a beautiful woman appear, then you begin to see the relevance of that odd waving and flailing about.
If you take this one step further and have a beautiful woman witness the odd waving and recognize it as the gesture that accompanies a magical spell, then the odd gesture has an effect on another character and maybe on the story as a whole. Maybe the beautiful woman, believing the delusional guy is a sorcerer, befriends him and takes him on a wild adventure with her because she believes he can use his powers to help her.
So now the event works - we understand why the event occurs (the guy is schizophrenic with delusions of being a sorcerer), and we understand what effect the event has - it leads to a grand misunderstanding and an even grander adventure. You've connected the event to both the past and the future.
You must do the same thing to your dialogue - all of your dialogue. Damon and Affleck do this with Will's dialogue in the Harvard bar scene. The dialogue results from who their character is, where he comes from, the events in his past, and his relationship to the characters in the bar and even to the bar and the university and the area of town and the economic and social class of the people in the bar and in that area of town.
Similarly, Damon and Affleck not only create repercussion from the hero's dialogue, they create the entire rest of the story from it. Because he showed off his intellect and his loyalty to friends and his apparent peaceful way of dealing with adversity in this scene in front of Minnie Driver's character in the bar, Will brings her into his life and she has the most profound effect of anyone in the script with the possible exception of Robin Williams' psychiatrist character. Will, in fact, ends up leaving his entire life behind to be with this woman in front of which he just showed off with this dialogue.
So you want brilliant dialogue? Make it the only dialogue your character can possibly say given who he or she is, where he or she is, and to whom he or she is saying it. Then make sure you have all your ducks in a row - every event leading up to the dialogue should be believable and every event after the dialogue should be at least partly a result of that dialogue. Finally, make us care about the character so that we've got a vested interest in what he or she is saying, and in the results of what he or she says.
Do these things and you will find people responding to your dialogue more deeply and excitedly than they ever have. One or two of them might even say that it's brilliant.