In movies, we should let actions and visuals replace talk
(Eg)
In nature films, the narrators do not say "Oh look, there's a beaver. He's getting out of the stream. He's going up to a tree. He's chewing it down."
Rather, the narrator talks about the ecological state of the valley etc.
Narration serves as a complementary counterpoint to the visuals, which gives information that is not readily available in the visuals, thereby elevating the whole story you want the scene to provide.
(Eg)
Jack Nicholson improvising. His improvisation was inventive. When he was given a situation, he would not improvise on the nose. Instead, he would talk around the problem. And good dialogue is the same. It's not explicit.
Take a banal situation for example. A guy trying to seduce a girl. He talks about everything but seduction. Anything from a rubber duck he had as a kid to the food on the table. But everything is all oriented toward trying to fuck this girl,
but it's not on the nose.
GOOD DIALOGUE ILLUMINATES WHAT THE CHARACTER IS NOT SAYING.
The 180 Degree Dialogue
Remember when you were developing your story, taking the obvious and turning it 180 degrees? You can use that technique to help with writing or polishing dialogue.
Take the most obvious line the character can say, and flip it upside down. Instead of "I love you," "I hate you."
See where that takes the moment. Sometimes a concrete wall, sometimes gold. It's always worth a try when you struggle for that perfect line.
Less is More Dialogue
If your character can say something in 6 words rather than 7, take out the extra word.
The actors will appreciate it too, as there will be more to emotionally act because there's less dialogue to speak.
Reality Dialogue and Movie Dialogue
Dialogue in Reality is often boring, and is not made for good movies. Listen to your own dialogue, it may sparkle in real life, but not on screen.
Instead, your dialogue must give the illusion of reality, rather than reality itself.
Audiences want the "illusion" of reality in movies, same goes for dialogue.
EG. The Godfather series. It wasn't reality but the audience bought it as a brilliant illusion of reality. That's screenwriting dialogue goal.
Obscure Dialogue
Never write dialogue only a few can understand.
You want your audience to be lost in what they're seeing, not having to tell their seatmates they don't know what was just said, or worse, having them to explain it.
Let the Actors Act *
Very often, writers tend to write superfluous dialogue that actors can just communicate with a look or gesture. Facial expressions and action can cut through so much talk.
Use dialogue that is subtle enough so that audiences can get it. This kind of writing allows the audience to write the lines, fill in the blanks, and participate in the character's inner thoughts and conflict.
Expositional Dialogue
Disguise exposition with chases, lovemaking, arguments, action, etc.
Again, with exposition, less is more, and not being on the nose.
People don't speak expositionally in real life. They rarely say things like "You're a wonderful person. I'm having a great time. I think highly of you and I'd like to marry you and have children."
Try for the kind of dialogue that seems ordinary, but is filled with emotion underneath. Adding in some action would help with this.
DESCRIPTION
Scripts are not the forum to impress people with your literary genius.
Stay away from superfluous, gratuitous writing.
Once again, less is more!
Also remember that you cannot shoot adjectives. Don't include adjectives and elements in the description that we can't see on film.
(EG) extra backstory, unplayable attitudes, references to outside events, etc.