9. Know Your Story
A lot of screenwriters set out to write their screenplays without a clear indication of what's going to happen. They have the germ of a good idea, and think that "freeing themselves" of limitations is a good way to start. And you know what? It's not a terrible idea to start that way, if you're happy to throw out almost everything you've written when you reach page 90. Thing is, screenplays adhere to more of a "structure" than people seem to realise. There are rules, and cues, and set points for things to occur that producers and executives like to see. You don't have to follow them, of course, and many writers - most famously, Quentin Tarantino - don't. But planning your story beats and knowing where you're writing massively important, because screenwriting is all about trimming the fat of your story to make it as streamlined and efficient as possible. How can you manage that if you're writing scenes that are working towards a goal that you're yet to discover? This writer certainly finds it helpful to just write and see what happens, and many novelists work in this way, too. But you should always ensure that your act breaks and (most importantly) ending are clear, because - like your characters - you need a goal to shoot for. Without it, you're just writing a collection of scenes with no clear purpose. Which brings us nicely to...