Well, I have finished 6 full-length (actually a couple of them are longer) movie scripts, and am working on a 7th.
I found this site because I wrote a prequel/sequel to the movie about the beautiful young lady, Christine.
So far I can't find any agent to read my stories, and have been trying for a long time, so I'm going to novelize one of the scripts and self publish it (in print form) to try for some exposure.
Having said all that, and I realize this is an old thread, what kinds of questions do you have?
A real good place to start would be "Screenwriting Tricks of the Trade", by William Froug:
Screenwriting Tricks of the Trade: William Froug: 9781879505131: Amazon.com: Books
One of the good pieces of advice in the book is to watch lots of movies, even bad ones, to gain insight into how the script translates into the story on the screen.
A dedicated screenwriting program is an absolute requirement. I recently upgraded to Movie Magic Screenwriter, which has the advantage of generating PDF's of the entire script, or of individual pages. It can also work in Novel format.
As with any software, pay a little extra and get a physical copy of the DVD for the software, rather than downloading a copy from the site.
Always make multiple backups of your work, 2 is good, 3 is better. Use CD’s or DVD’s for these backups, not flash drives (can die in a…flash), or hard drives (will die eventually).
Keep one of these copies in a different location, such as a safe-deposit box. Don’t try to be lazy about these backups, or you will be crying a long river of tears.
Everybody is different. It usually takes me about 6 months to 2 years to complete a script, although I did the sequel in 8-10 weeks. I must have been thinking about the story for a while. I wrote the entire thing in my head, while working on the assembly line (don’t worry, I was careful; some operations can be done with little mental input, once things are flowing), and transcribed that night’s thoughts when I got home.
I have gone back and touched up my older stories, after getting some more experience under my belt. Screenwriting textbooks (I have found Froug's to be the best of the several I have read) stress that most of writing is rewriting, and that is true. I usually rewrite each script about 50 [fifty] times. I find that each time, I change a little bit less. Eventually, I will reread the entire story from beginning to end, and find nothing else to change, and that is when I know it is ready for prime time. Even then, I will occasionally go back and make minor changes, a few months later.
I personally find the screenwriting format easier than the novel one, but that is just me.
In a screenplay, as opposed to a novel, you can not directly describe what the characters are thinking. This can only be revealed through their actions. That is not as much of a barrier as you might think.
Hope that helps a little.
