Hey buddy,
Good luck on your writing goals. I haven't read the book you mentioned, but there are just too many how-to guides for me to sample them all. Here's a couple of things to keep in mind regarding screenplays:
- Format is important. Movie format is different from sit-com format which is different from stageplay format. Make sure you brush up on the subtle differences for the type of screenplay you want to write.
- Unless you are planning on directing your own play, leave out camera angles, zooming suggestions, and other directorial type comments. These will not endear you to any studio.
- Write tight, direct prose for your scene descriptions. Think short and to the point.
One book that I think all fiction writers should read at one time or another is The Writer's Journey: Mythic Structure for Writers. It was written by the writer of the movie Lion King, and basically takes Joseph Cambell's classic 1000 faces of a hero and relates that to screenwriting.
I don't currently have an agent for screenwriting. At this point, I'm not sure if I want to pursue commercial avenues with my screenwriting. I'm simply trying it out and seeing if it's a medium I care to work in.
If you want to get a quick lesson in formatting screenplays, check out Intro to Screenwriting and How To Format A Screenplay. They both have enough information to get you up and going fast.
Most of all, grab your dreams by the horn and hold on for the ride of your life.