I'll try anything, Jeff. In the world of writing anyway.

Quoted from eldave1 There are probably as many approaches as there are writers. For me, it kind of goes in this order: 1. What is the theme? Moral of the Story? This can range from the obvious, tried and true (e.g., don't judge a book by it's cover, love conquers all) to more subtle. The point being - I have to get the moral of the story set in my mind before I start doing anything else. 2. Who is the main Protag and the main Antag. 3. What is the Protag's goal and what is the barrier. How does the Antag play into that barrier 4. What happens to my character if they achieve that goal. What happens if they don't. Those are my four basic steps. The ones after those really vary depending on how much steps 1-4 get me into the story. Sometime I can blow right ahead without an outline - other times - not so much.

Thanks Everyone for your responses. I see a good variety of different approaches.

That being said thanks eldave1 - your approach is what I was sort of looking for...that's how my brain works! I need plan everything out. I do a spreadsheet every time I take a holiday!  

One key organisational tool, similar to theme, is something Truby mentions and I haven't seen anywhere else:

The idea that everyone in the script, though you don't realise it at the time, is after the same thing.

It can be a Macguffin...Like everyone chasing the Holy Ark in Indiana Jones, or it can be something more vague...to fit in perhaps, freedom, control or to achieve happiness, but in professional stories everyone is ultimately after the same thing, they just try and get it in different ways.

This is something that a lot of amateur scripts lack, which is why they seem unfocused. If they're not after the same thing, they belong in different stories.

I feel my process is way less developed/complicated (I don't mean that in a braggy way -- I mean that in a "I'm disorganised" way).

My initial ideas are always a character and they're doing something, which becomes a scene in the script/story whatever. I write that scene first.

I'll write every scene before and after it with the idea that they're expendable, and the central scene can't be removed. It helps retain the theme I intended and doesn't let me get off track because there's something sticking me in one place.

This is super dark, but I think it explains. I had an idea based on something I encountered in my line of work -- in which a woman convinced her son to continue letting himself be molested so their family could benefit. I imagined what that conversation, if any, would look like, and wrote it. The rest of the short formed around it.