I am a huge believer in backwards writing. If there’s a more officially-accepted term for this practice, I have yet to hear it, so for me, it’s backwards writing.
Backwards writing is the idea that some of the first scenes you write should be some of the later scenes in your script. I strongly believe that it’s virtually impossible to know what your beginning should look like when you don’t know your ending. That’s why revising is so important: there’s no way you could’ve possibly known what ACT 1 really needed to be if you hadn’t written the ending yet.
Now I don’t recommend being overly literal with this method. I’m not arguing that the first scene should be the very last thing you write either. I am saying you need to liberate yourself from the notion that you will ever sit down and write a script beginning on page 1 and ending on page 100 exactly in that order.
One thing you might want to try is writing whatever you consider to be the most pivotal scenes first. Maybe you know two characters are going to fall in love, or maybe that they’ll break up. Maybe you know that at some point, character A is going to murder character B. Maybe you have an M. Night Shyamalan style plot twist planned. If so, THAT is the scene you write first. After you have it written it you can ask yourself “ok, now what would my audience need to know for this scene to have as much impact as I want it to?” Now you have ideas for other scenes leading up to the pivotal scene.
The incredibly important part of backwards writing is that your writing be actual script writing, not outlining. There seems to be this misconception that writing the perfect outline is a prerequisite for writing the perfect script. I’ve always found that the process isn’t that linear. A good outline can certainly help you determine what scenes to write, but at the same time good scenes can also help inform what your outline should look like. I’ve lost track of how many wonderful ideas became immediately obvious to me while I was writing that never came to me when I was just “brainstorming” or “outlining.”
It’s okay to go ahead and write scenes even if you haven’t made final decisions on all the structure (Writers making ‘final’ decisions is actually a bit comical tbh). It’s okay, if not downright necessary, to write scenes even if you haven’t written all the scenes that will precede it. Try writing backwards. Sometimes it’s the only way to move forwards.