I just finished helping judge a screenwriting contest and the two biggest issues were:
Character-you must know your character and write in “their” voice not in yours. Yes you have to have a voice. Many great screenwriters have a voice, but every character is unique. Dialogue is such a huge part of character. I used to teach a class on it, I haven’t done it again, but can always go over dialogue with you for a discounted rate. It’s important, really important.
Also in character, writers weren’t describing their characters. You NEED to describe them-what they are wearing, what they look like. Don’t tell us who they are, describe them or show us.
Story-you must know what story you are telling. I read so many scripts with great premise but no story. Other issues were; bad first 10 pages-in reality a reader won’t go past page 5 if they don’t have to. Make those first pages count. Voice overs and flashbacks-get rid of them until you are established. Pacing-if you don’t know how to pace a story use Save the Cat or Contour to help you-I know it sounds weird, but when reading a lot of scripts, it is easy to get bored and want to move on-which will be a “pass”. Just thought I would share this insight, hope it helps. We all have these issues for sure.
Sadly you have to get past the reader. Readers are bored easily and since they have tons and tons of scripts to read, it is really easy to not get through a script that probably would make a great film.
My advice is if you have the means, get your scripts covered. Join screenwriting groups and get your scripts reviewed by your peers, take classes and don’t be afraid to get rid of that genius scene if you need to.
Don’t submit your first draft to contests. I am sad to say that even I did that in the past. It’s not a good idea.
Don’t ever write on the cover page or last page “million dollar award winning screenplay”. That’s like bragging about your I.Q. If it was true, you wouldn’t need to.
Use common sense people and you will get read, make these mistakes and I can pretty much promise that you will end up in the deleted emails, or waste basket by page 5.
Good luck and happy writing!