Most people approach screenwriting backwards.
I spent six years reading specs that would make a grown producer weep into their decaf latte. The bad ones all share the same DNA. They just express it differently. Let me show you the patterns so you can avoid them or recognize them when someone sends you their "magnum opus" at 2 AM. Screenplays are blueprints, not literature. This is the single most misunderstood concept in the industry. People write about characters feeling sad instead of writing what the character does when they're sad. A tear rolling down a cheek is a direction for the actor, not the writer. It tells you nothing. "He stares at the phone for forty-five seconds before deleting the draft he just wrote" tells you everything about grief, self-censorship, and hesitation. Show the behavior. Trust the reader to infer the emotion. I once read a spec where the protagonist experienced existential dread. Seven pages of internal monologue delivered through voiceover that basically summarized the entire third act before page ten. The reader had no reason to keep going because the emotional journey was already over. Voiceover is fine when it adds information the visuals can't convey on their own. Otherwise it's a crutch for writers who don't know how to dramatize thought.
Action lines should be lean. Two to three lines per paragraph maximum. Write what the camera sees, not what the character thinks or feels. When you write "John feels conflicted about whether to pull the trigger," you're doing everyone's job for them. The actor will figure out conflicted. The director will figure out conflicted. Your job is to give them something concrete: John's hand trembles as he raises the gun, then lowers it, then raises it again. Three beats. That's a scene. Dialogue has the same problem. People talk in paragraphs in their specs because they haven't learned to cut. Real dialogue is fragmented, interrupted, and full of things left unsaid. When two characters say exactly what they mean in complete sentences, it reads like a therapy session disguised as drama. Subtext is not a literary device. It's how human communication actually works. I dealt with a script where every supporting character had a backstory explained in their first appearance. A barista who used to be a concert cellist. A cop who had a strained relationship with his father. None of it served the plot. It was character wallpaper, and it bled the pace dry. Backstory belongs in the writer's head, not on the page. If it doesn't change the scene's outcome, it doesn't belong in the screenplay.
Scene transitions are another common failure point. Writers paste in "meanwhile" and "later" like they're padding a college essay. Cut to black when a scene ends. Let the next scene open on its own image. You don't need signposts telling the reader when time has passed. The script will tell you if the next beat is a new time or place through the action lines. Formatting matters more than most writers think. Courier 12-point, one page equals roughly one minute of screen time. If your script is 140 pages, you have a problem. Not because 140 is inherently bad, but because anything over 120 signals that the writer cannot prune. A tight 90-page script about one thing beats a bloated 120-page script about five things every time. Studios gatekeep based on page count alone. A 110-page rookie spec gets read. A 140-page one gets archived without a second look. The worst mistake I see is writers trying to write the movie they want to see rather than the movie they can actually shoot. Big explosions. Period costumes. Ten locations. If your opening scene requires a military helicopter and a crowd of 200 extras, you're not writing a screenplay. You're writing a fantasy. The best indie scripts I ever worked with were set in one apartment with three characters and a locked door. Constraints force creativity. Unlimited budgets force laziness.
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Another counter-intuitive thing: characters don't need to be likable. They need to be compelling. We've been told for decades that audiences want to root for their protagonists. That's half true. Audiences want to watch someone want something with enough intensity that you can't look away. Anthony Hopkins in Silence of the Lambs. Tony Soprano. Walter White. None of them are good people. All of them are impossible to stop watching because their goals are specific, urgent, and obstacles are real. Plot is not the same as story. A plot is a sequence of events. A story is what those events mean to the characters. Most bad screenplays have strong plots and weak stories. The hero defeats the villain. Great. Why should we care? What does winning cost them? What do they lose along the way? The emotional price of the external goal is what turns a competent script into something you'd actually pay to see. I had a friend whose script had a perfectly structured three-act plot. Everything hit the beat. Inciting incident on page 12. First plot point on page 25. Midpoint on page 55. Final act on page 85. It still got rejected by every reader who saw it. The reason was that the protagonist never changed. He started as a coward and ended as a hero, sure, but the script never made him earn it. Every victory came from outside forces. External solutions to internal problems. That's lazy writing regardless of how many boxes you checked.
Let me address one thing that nobody wants to hear: rewriting is where actual screenwriting happens. The first draft is just you proving to yourself that the story exists. The second draft is you figuring out what the story actually is. The third draft is where you cut the scenes that aren't earning their place on the page. I've seen writers spend three weeks on a first draft and zero hours revising. That's not a work ethic problem. It's a fundamental misunderstanding of the craft. A polished first draft is a myth. If yours looks polished, you probably haven't cut hard enough. Specific technical note about scene structure. Every scene needs a shift in value. The character should enter the scene in one emotional state and leave in another. If the scene starts with the character wanting something and ends with them still wanting the same thing in the same way, the scene is doing nothing. Cut it or rewrite it. This applies even to transitional scenes. Even quiet moments need a turn, however small. I've also learned the hard way that your logline should be one sentence and it should contain the protagonist, the central conflict, and the stakes. "A man fights a shark" works. "A man fights his inner demons while dealing with a shark" doesn't because now you have two stories and neither of them gets developed properly. Loglines that try to capture everything end up capturing nothing. Pick the spine of your story and build from there.
One more practical thing that separates working scripts from unreadable ones: page one matters more than you think. If your opening scene is a montage, a title card, or someone waking up and checking their phone, you've already lost the reader. Start in the middle of something happening. Give me a question I need answered by page three. Not a mystery. Just a question. Why is this person running? Why are they hiding? Why did they just punch this guy in the face? The biggest bottleneck in getting a screenplay read is not quality. It's the sheer volume of submissions. Readers process maybe fifty to a hundred scripts a week. They skim. They skip. If your first five pages don't demonstrate that you understand the form, they will not invest the time to figure out if you learn later. This isn't cruel. It's economic. You have five pages to prove you're worth the read. Make them count.
