Is it a movie?
That is the question writers need to ask before they begin writing a script. Boring the reader or viewer is the cardinal sin. People yawning in a movie theater is a sure sign of a movie that never should have been made.
Some people think they have a great idea for a movie, but they don't develop it beyond the idea. I've read several scripts over the years that were about as exciting and entertaining as watching a tree grow. Watching a tree grow in the forest, where no one can see it, and where scripts like that are buried, hopefully forever.
Many of the scripts I've read fall far short of an affirmative answer to this question. It is in the comedy genre that this occurs most often. Someone wants to write a comedy or romantic comedy screenplay, but the result is a series of comedy skits strung together to fill up the script. This is not a movie, it's a variety show.
A movie requires an actual story with a beginning, middle and end. And the progression of the story must be apparent, as well as some change in the protagonist's character. The protagonist should learn something on his/her journey through the "story world" of the movie. Even in a comedy, the protagonist must change or grow in some way, usually emotionally.
Comedies seem to have sunk the lowest over the years. Most depend on a series of marginally amusing sex jokes, and most carry on the jokes beyond the point where they are amusing. And most contrive preposterous situations that, even for a comedy, are too absurd to accept. Even if you are playing for laughs, don't insult my intelligence by doing something I know is wrong. Don't violate the rules of logic unless that is a part of your plot. But don't do it because you as a writer are too lazy to concoct a superior script.
An idea isn't a movie. A few exciting or funny scenes isn't a movie. A movie is a fully realized story.
I've provided coverage for S3 Entertainment, the Just Effing Entertain Me Screenwriting Competition twice, the Nevada Film Commission, and am currently providing coverage for You Go Far Productions, Ltd., a film production company in London, England. I also moderate the Ann Arbor Screenwriting Group in Ann Arbor, Michigan.
I'll be teaching Professional-Level Screenwriting at the Meijer Branch of the Jackson District Library Tuesday, April 7 & Tuesday, April 21, from 1:30 PM to 3:30 PM in Jackson, Michigan.