1. Become an eavesdropper: I lived for many years in New York City, and one of the great things about it is New Yorkers talk in public as if they are in a totally private space. I live in Miami now and it’s not quite the same, though for some reason it’s close to the New York experience when people talk on cell phones. On the bus one day I heard a guy talk to a friend about a messy custody battle he was engaged in. He did not spare any details.
Don’t eavesdrop just to be nosy (though that is a side-benefit–you’ll get story ideas). Learn to analyze the way people express themselves. Try to come to conclusions about the people speaking from the way they speak, not just from the literal words they say. Take note of what people DON’T say.
If someone has an interesting accent, think about how you can suggest it subtly in written dialogue. (Nothing is worse than reading a passage of dialogue where a writer is doing a poor job of approximating an accent. Usually, it’s because they overdid it.) Notice the rhythm of people’s speech. Note regional and generational slang.
2. About slang: If you’re writing a contemporary story, use it sparingly, because nothing dates a story faster. If you’re writing an historical story, research the slang of the time and place, but again, use sparingly. Don’t slap a ton of “It’s the bees knees!” and “That’s the cat’s pajamas!” all over a story about the 1920s, for instance.
When you’re writing something futuristic, you basically have to invent slang. Which can be a lot of fun, actually. (I think James Dashner, who wrote The Maze Runner series, overdid it a bit, though kids who’ve read the books seem to love the invented slang.)
It bugs me when I read an historical novel with modern-day slang in it. But it’s also annoying in futuristic stories. Keep in mind that language is always evolving. That’s one reason older people get exasperated listening to teens talk to each other.
3. He said, she said. The prevailing wisdom is to only use he said, she said as dialogue tags. I don’t disagree, but also don’t think you’ll be struck down by the dialogue gods if you mix it up a bit. After a while, he said, she said becomes BORING. I listen to a lot of audio books and for some reason I notice the dialogue tags a lot more. It can really get on my nerves after a while.
Don’t use tags like “he smiled” or “she pouted.” You can’t smile or pout dialogue. But something like “she shouted” or “he whispered.” is O.K., because you can shout and whisper dialogue. But for the most part, stick to he said, she said.
4. Don’t let all your characters’ dialogue sound the same. When I wrote about creating characters, I mentioned that EVERYTHING pertains to character. This is especially true of how they talk. Age, education, where they grew up, their personality (shy, ebullient, pompous, insecure, etc.), state of mind–all these things and more should impact on how your characters speak.
5. Avoid perfect grammar. Unless your character is an English teacher.
Scratch that. An English teacher who speaks perfect grammar is a cliche. Maybe when she’s not with her students she swears a lot. Or reverts to the Brooklyn accent from her childhood.
Characters speaking in perfectly grammatical sentences will come across as stilted and unrealistic. Let each character murder the language in their own special way.
6. Avoid “on the nose” dialogue. This is a screenwriting term, but it also pertains to writing other kinds of fiction. On the nose means the characters are expressing their exact thoughts and emotions. Like this:
“Oh Roderick, I hate you now that I know about you and Cynthia and will plot to bring about your destruction . . .”
That’s a bit of an exaggeration, of course, but on the nose really does sound that silly. It would be far more effective to create dialogue that has subtext:
“Roderick, darling. You’ve brought Cynthia to the party. How thrilling.”
O.K., that’s still a bit overdone, but it’s just to give you the idea. Within the proper context, you can convey what the character feels through dialogue without spelling it out to the reader.
7. Avoid too much exposition. You’ll end up with long talking head scenes. There are times when it’s appropriate (i.e. Miss Marple exposing the murderer) but it’s usually best to keep expository dialogue down to a minimum.
8. Read your dialogue aloud. Better yet, tape yourself speaking the dialogue and play it back. Or, if that’s too old-fashioned, get text-to-speech software. I recommend NaturalReader. (There is a free version.) Listening to your dialogue will help you catch anything that reads as stilted or unrealistic.