Writing a script is very different from watching a film, so before you think about writing your own, it is a good idea to read several screenplays. It is also helpful to take scriptwriting seminars and workshops; to attend screenwriter's panels; and to watch special features on DVDs and listen to the Director/Writer audio track.

Formatting is very specific, but actually easy: use Final Draft 6 software, the industry standard.

A great many of the books on screenwriting say the same thing, so beware. Here are a few classics:

Robert McKee. Story: Substance, Structure, Style and The Principles of Screenwriting. In addition, his seminars are legendary.

Syd Field. Screenplay : The Foundations of Screenwriting; A step-by-step guide from concept to finished script.

Syd Field. The Screenwriter's Problem Solver : How to Recognize, Identify, and Define Screenwriting Problems.

Denny Martin Flinn. How NOT to Write a Screenplay: 101 Common Mistakes Most Screenwriters Make.

Other books available on Amazon.com.

Get to know the film business. 'Variety' and 'Entertainment Weekly' will keep you up on what is happening in the field.