New to screenwriting? The Hollywood Standard tells you how to format a script. Final Draft is a software program that helps you format a script. Once you learn formatting and digest the required reading, you'll be good to go. (Actually, you may want to begin outlining and writing small sections while you read.)

Formatting

Riley, Christopher. The Hollywood Standard, 2nd Edition (Studio City: Michael Wiese, 2009).
Final Draft (which can be purchased from www.finaldraft.com, or at the Writer's Store).

Required Reading(In This Order)

Snyder, Blake. Save The Cat! (Studio City: Michael Wiese, 2005).
Egri, Lajos. The Art of Dramatic Writing (New York: Simon & Schuster, 2004).
Vogler, Christopher. The Writer's Journey (Studio City: Michael Wiese, 2007).

Suggested Reading

Akers, William. Your Screenplay Sucks! (Studio City: Michael Wiese, 2008).
McKee, Robert. Story (New York: Harper, 1997).
Seger, Linda. Making a Good Script Great (Hollywood: Samuel French, 1994).
Sweet, Jeffrey. The Dramatist's Toolkit (Portsmouth: Heinemann, 1993).
Syd Field was a master screenwriter. You may want to check out his works.

Stores

The Writer's Store in Los Angeles has nearly any resource you could ever want.
Samuel French bookshops contain some writing materials, but mainly resources for stage actors and playwrites.