Write your idea in the form of an outline on your computer or notebook. Detailed outlines can help a writer organize their thoughts. This can be from 50 to 100 lines in length. Each line is about what forms your story.
Narrate your story on notebook paper or computer. After you have outlined your story, expand on it by writing eight to 15 pages, providing the beginning, middle and end. Story is what drives the script. You must know it detailed from beginning to end. This will also help you identify problems in your script and rework them. A good book to read is "Story" by Robert McKee, renowned for his work in scriptwriting, producing and lectures on story for screen.
Talk to yourself with a tape recorder, or write it all down in a journal. There is no right way to remember those midday epiphanies, but this will help you build the tools you need to apply in creating your script.
Format your script by using 8 1/2-by-11 inch paper, with a page number located in the top right hand corner, beginning with page 2. The first page is never numbered. The top and bottom margins are between half an inch and 1 inch. The left margin is between 1.2 and 1.6 inches. The right margin is between half an inch and 1 inch.
11-point Courier New is the only acceptable, professional-style font for a screenplay format and type size. Another font will not make you stand out; it will only make you look like an amateur.
Write to the pace of one minute per page. A screenplay is between 80 and 120 pages, depending on the length of your stage directions or action. Cut the fat. No one wants to read a 180-page script, even if it's epic. Linda Seger, a script consultant and screenwriting coach, best explains how to rewrite and "cut fat" in her book, "Making A Good Script Great."
Write a scene heading for each scene. Scene headings will tell the reader where the action takes place. For instance, if characters are in a hotel having breakfast, it will read:
INT. HOTEL-MORNING
If you are having dinner, replace the word morning with night. The scene heading is always located in all caps to the left of the margin. Each time you move to a new location, include a new scene heading. If there is no time lapse, these should be marked with the word "continuous" like so:
INT. HALLWAY-MORNING CONTINUOUS
Write stage directions or action under the scene heading to give the reader or actor an idea of where they are. The direction/action you write moves the story, not the dialogue. Be direct. You do not need to flower the paragraphs with adverbs that do not show action.
Center the names of each character on the page. The names must appear in all capital letters, with dialogue centered underneath. If your character is crying, for instance, you can add a parenthetical. A parenthetical phrase should appear under the character name, in parentheses, above the dialogue instead of a full line of stage direction:
KYLIE
(crying)
Please, don't go Andy! I love you.
Transition from scene to scene by writing "Fade to Black" or "Fade Out." Transitions appear in the right margin, one line under the last set of dialogue, and can help you be clear as to how the action moves along. Be sparing with these. Most directors will make the decisions for you.
Print a copy of your finished script, read through it, then rewrite the script. Rewriting is the most important part of the process. Look at the dialogue. Does it sound awkward or seem to trip you up when reading it? Change it. Does your scene seem to go on for eight pages and not really carry the story. Delete it. All of it. Be prepared to write up to 15 or more drafts of your masterpiece before it is well written.