How important is it to stick to the rules?

You need first of all to know that a brilliantly written film script will not fail to impress simply because it is incorrectly presented; any more than correct presentation will be the salvation of a mediocre one.

That said, there are very good reasons why a screenwriter should take the relatively small amount of trouble required to master a few of the fundamental screenwriting conventions:

It is a signal of professionalism that predisposes other professionals to take the writer seriously.

By using and exploiting a shared and established "language", your instructions are less likely to be misunderstood.

A correctly formatted script is usually more readable. That is why formatting conventions were developed in the first place.

How do I know what to include?

It is important to understand the stages that a script goes through once it has been successfully submitted to a production company so that you know where your job ends and someone else takes over.

The Submission Script is the one that you send in and the only one that you really need to worry about. Ideally it should be as plain vanilla as possible.

Don't be tempted to include any kind of introduction. The next page, after the title page, should have your first scene on it.

Don't include separate cast lists or character descriptions; these last should be integrated into the script.

Don't number the scenes. This will be done when it is re-typed by a production secretary and becomes a Production Script

Here are a few other tips for creating the right impression:

Type or print on one side of A4 paper using a readable, preferably monospaced, typeface.

The title page should include, the script title, your name and contact number; absolutely no graphics or logos.

Avoid fancy binders. To protect your script, punch it with an ordinary two hole punch and bind it between cover-boards ; fastened with two staple pins.