READING SCREENPLAYS WILL HELP IMPROVE YOUR WRITING (PART 1)
A lot of "so-called" writers don't read scripts. It's very important to read scripts.
FORMATTING
One comment I always here, from novice screenwriters, is that they don't have the foggiest idea how to properly format a script.
The best way to learn about formatting and how to write a screenplay, in addition to reading books on screenplay formatting and taking courses, is to read scripts.
READING SCREENPLAY WILL HELP IMPROVER YOUR WRITING (PART 2)
SCREENWRITING EXERCISE
Watch a film.
Watch the "nonverbal moments" that occurs during the film.
Read the screenplay version of that film.
Analyze how the "nonverbal moments," in that particular film, were written in the screenplay.
How were the "nonverbal moments" communicated without the use of dialogue?
This exercise is very helpful in assisting writers with learning how to use description versus relying too often on dialogue to tell a story.