Read Screenplays
Along with writing outlines, the best thing you can possibly do in order to master the craft is to read screenplays.

Yes, we know reading films is not as much fun as watching them, but it all depends on the level of commitment you’re willing to put in to making a career as a screenwriter. Those that write everyday, write outlines and read scripts are simply more likely to than those that don’t.
We’ve seen a remarkable improvement in some of our writer’s work after 6 months of solid screenplay reading. Aim to read two screenplays a week and slowly build it up until you’re reading six or seven. Do this for a year and you’re golden.
Obviously, there are too many scripts out there to read them all so concentrate (at first) on reading those within the genre you write. If you’re writing an action spec, for example, stop writing it until you’ve read The Bourne Identity by W Blake Herron and Tony Gilroy.
Read the classics within you’re chosen genre to really get a feel for how the writer communicates in words what you see on the screen. You can’t go wrong by reading anything by Billy Wilder, Woody Allen, Robert Towne, or William Goldman, to name a few, but total immersion in your chosen genre(s) is a must.
Reading screenplays is particularly good for absorbing the rhythms of dialogue and understanding what makes great description. All manner of tricks and techniques become apparent after reading a number of scripts, and the great thing is they all become imbibed into your own writing.
Another tip is to read a screenplay at the same time as watching the film. Stop the film every time it comes to a great scene and analyze it.
Write up a list of the screenplays you need to read and cross them off as you go along. This will give you a sense of progression as you work through them, and a mini “course” to complete that’s as enlightening as any at USC.