Screenplay essentials

1. Story and Character A screenplay starts from a High Concept idea, from the development of an unforgettable character, or in the best case from both.
2. Outline Before Writing Know at least how the story ends, begins, as well as the screenplay’s five major plot points before writing the script.
3. Three-Act Structure The experts can debate sequences, but all agree the story is told in three acts, with a turning-point to end Act I and II.
4. Original Voice Clear and concise writing is key, keeping action description at four lines or less, but the action should still sound original.
5. Screenplay Form Professional screenplay format is a must as well as correct page appearance: lots of white space, no “I” pages, and block pages.
6. “What happens next?” All scenes must move the story forward, reveal character, or both. Any scene that does neither are not necessary and should be cut.
7. Short Scenes A screenplay must move fast, so three pages should be the absolute maximum before you cut to a new location. Half a page is typical.
8. Brief Dialogue Remember, film is a visual medium. You show the story. Never tell it through verbal storytelling. Keep lines of dialogue short.
9. Under 120 pages One script page equals one film minute, so a drama is about two hours (120 pages); a comedy is closer to 90 minutes (90 pages).
10. Know the Logline In one sentence, you must be able to pitch “what the story is about,” and make a comparison to other successful Hollywood films.
Source: http://thescriptlab.com/screenwriting-101/screenplay/what-is-a-screenplay/636-top-ten-screenplay-essentials