18. Nobody Wants To Read All Those "Realistic" Conversations
Yeah, we get it: you wanted to write something like the Quarter Pounder with Cheese conversation from Pulp Fiction, right? Unfortunately, you're not Quentin Tarantino, so nobody wants to read any scenes where your characters are sitting around shooting the sh*t UNLESS it advances the story. It doesn't matter how "real" or natural you think your conversations are... if it ain't relevant, CUT 'EM.
17. Writing What Can't Be Seen Or Heard
Everything you put in your script absolutely, fundamentally has to be able to be seen or heard on the screen, so including details that only serve a purpose on the page is a big-no-no. If you start outlining your character's complicated history in the script, you're wasting your time: if the audiences can't see or hear what you've written down, it has zero place in your screenplay.