Here's a screenwriting exercise I came up with to help myself get better with writing screenplays. You can argue the worth of it, but since starting it I've seen my skills improve.
You can do this with either a full length movie or a tv show(preferably a show meant for a 30 minute block). Now turn off the volume, and watch the movie with a pen and paper or your laptop. What you are going to do is write the script for this show or movie. That's right, you are the screenwriter now to your favorite show. I want you to write and format this script just like you would any other screenplay.
When you watch it you can make up your dialogue or use the dialogue from the movie. I recommend doing both on separate shows/movies. What is important is seeing how your script compares to the real professional script, so if you can get a copy of the screenplay to read after the rewrite, all the better.
This exercise works best with movies you haven't watched before, but it can still be done with ones you've already seen.
What you want to learn from this exercise is your wordiness, your descriptions, and your actions you use to describe events that happen in the play. If you are replacing dialogue you want to see how your dialogue sounds. Read it out loud and then read the same lines of the movie and see how they compare. How does your rewrite compare to the original? Are they similar in length? Do you use too many words or not enough?
Seeing how you write compared to others reveals flaws in your writing that may not otherwise manifest themselves without them being pointed out. When I started doing this some of my mistakes just jumped out at me which I had never seen before doing this.
So, give it a try, and let me know how it works out for you.
