There are two reasons for writing a screenplay, first is as writer/director/producer, second is as a spec screenplay for sale to someone else to direct &/or produce.
If you're writing to direct/produce yourself there are no limitations on what your screenplay format should or shouldn't include.
Include everything you want to include.
Go crazy. You're the one reading it.
Do whatever you want.
If you're writing a spec(ulative) screenplay to put on the open market to sell to someone else to finance/direct/produce then your spec screenplay will be competing against MANY other spec screenplays.
For the poor guys that have to sit down and read fifty-bazillion spec screenplays keeping a tally of locations to secure, cast and crew requirements, equipment required, and other resources to budget for - for each screenplay - what they don't need to read is all sorts of crazy cr@p they're going to shoot with the locations they have, cast & crew they have, equipment they have, and other resources they have, and NOT the exact vision that you have.
There's no way for
you to know what it is that
someone else is going to do with that screenplay once they buy it.
Once they buy the rights from it - it's theirs, just like a car or couch. They can even sit on it and do nothing.
A screenplay is a blueprint that you as the architect have designed.
How the builder or homeowner chooses to execute the blueprint they have purchased from you is out of your control. They can change windows, doors, walls, railings, put in carpeting where you put in tiles, and stucco the siding instead of using brick.
It's their dime. You have no control.
Now, because these "readers" hafta pour over fifty-bazillion screenplays it sure is nice when they pretty much all follow some generally accepted industry conventions.
Thus: spec screenplay format.
Dialog is pretty much unlimited.
Characters need to say what they need to say.
Don't go hog-wild with dialects and abbreviated slang. Have your rednecks talk like rednecks and your foreigners muddle through broken English the best they can, but go easy on it.
Also, keep in mind there's a difference between FORMAT and STYLE.
Your screenplay editor should keep the dialog format pretty neat.
Your on-the-nose (OTN) and expository dialog is all your style to avoid.
Know the difference between V.O. and O.S.
Scene headings (slug lines) and action lines is where most new spec screenplay writers have trouble. And their title pages, too.
Scene headings are almost always three parts:
INT./EXT. (space) LOCATION (space hyphen space) DAY/NIGHT
Bold or not bold is your choice. Old school is not bold. Within the last decade bold slugs are only beginning to become acceptable.
Action lines should provide the most basic and minimal direction as possible short of being uninteresting and boring - which is a really neat trick to pull off!
It is an art to learn.
If the popcorn gobbling audience can't see it then don't write it.
Example
Code:
EXT. CITY SIDEWALK - DAY
On the way to his car Bob jaunts along thinking of the wild sex he had
with his boss last night.
Audience may know from the previous scene what Bob's thinking about, but you don't write in an action line what the audience doesn't see.
Code:
EXT. CITY SIDEWALK - DAY
On the way to his car Bob jaunts along with a self pleased grin.
Now consider how twenty different directors behind a camera are going to shoot that simple two second scene.
Hell, you can probably shoot that same scene eight different ways.
So, in a SPEC SCREENPLAY don't include camera angles, lighting, and all sorts of different gobbledygook you have no control over when someone else is paying for locations, cast & crew, equipment, and resources.
The title page and all the text throughout the entire screenplay are all 12point Courier.
DON'T do anything else.
12point Courier. That's it.
Here are some mostly current screenplays to read over:
http://www.imsdb.com/latest/
Most don't strictly follow spec screenplay format because most are by established writers who have the street cred to do whatever they want - within reason.
Some are even shooting scripts WHICH DO include camera angles and transition cuts.
But the more of these you read the better you'll understand what's expected
Also helpful is to pop in your top ten DVDs and watch the extra/bonus features, especially the director/actor/producer commentaries, and learn just how much changes from script to screen.
No one gives a flying fig about the writers.
My three goto DVD commentaries are for 'Cabin Fever', 'Fight Club', and 'The Expendables'.
I have no comment about the quality or content of the films themselves, but the commentaries are fantastically educational about what is and isn't important in the screenplay itself.
Another resource is to read the production wiki of 'Salt', then watch the movie, then reread the wiki and watch the DVD commentary if you can.
http://en.wikipedia.org/wiki/Salt_(2010_film)#Production
A lot changes from script to screen.
Watch enough of these commentaries of writer/director films and you'll see that even when writing to direct that what they imagine in their own screenplays gets changed when faced with the actualities of locations secured, cast & crew on hand, and other budgetary limitations.
If you've ever watched the deleted scenes of a film then you can consider the cost associated with not just writing a scene destined to be left on the proverbial cutting room floor but also to secure the location, assemble cast crew and equipment, shoot it, edit it only to ditch it.
Ten minutes of deleted scenes from a $40million 110min final edit film:
$40M production budget
/120min shot
= $333k per screen minute
x 10min deleted
= $3.33M basically thrown away on poor/safe planning, depending upon how you look at it.
And this is frequently by professionals who should know WTH they're doing.
So, be VERY judicious about what it is you're including in your spec screenplays.
Also, what screenplay editor program are you using?
