When I'm not editing Always Outnumbered, Never Outgunned, I'm in the process of accumulating notes for my next big writing project, tentatively titled The Fall Of The Hammer. On one side of the page (metaphorically speaking) I have the elements for the story — the people in it, what they want, what happens to them. On the other side of the page, I have a slew of ideas brought up by the ingredients in the story. My way of making the story about that stuff is to find all the ways the elements on both sides of the page can line up.
I don't expect things to come into alignment for a fair amount of time yet. The story is still protean, with a great many possibilities moving in and out of focus inside of it. Most tellingly, it's still difficult for me to explain it to others.
That last quality, I think, is the surest sign that a story is unformed. If you can't explain it to someone else while standing on one leg (hope you've got good muscle tone!), you probably don't know what it's about.
The Python programming language — which I used, by the way, to write the software that now powers this website and a couple of others* — has a principle that echoes this:
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
The same would seem to go for a story. Any story you can't concisely summarize, that you can't explain succinctly, isn't a story you understand. This doesn't mean the best stories are the ones that are concisely explained by anyone; this means a good metric for your understanding of your own story is how well you can boil it down into something that others can grasp and find intriguing.
I'm drawing this distinction because I think we have a tendency to assume it's best to aim for a story that requires the least amount of work to be explained. I don't believe that's true; I think it's important that we aim for the stories that we care about and that matter to us, and then work on ways to convey their essentials as effectively as we can.
There's no contradiction between these two missions. Thinking about what really matters in your story — why this story? why this way? — helps you find the things in it that make it most easily communicated to others.
Over the years I've grown to appreciate the value of attempting to explain your idea, in a succinct way, to your peers. Sometimes I've had insights into the real nature of the story right then and there, while standing on one leg, that I didn't have after hours at the keyboard. My current explanation for this is simple: When you're at the keyboard, you don't have to make decisions as urgently. You tend instead to accumulate possibilities and toy with them. When you're on the spot, you have to pick something, and you also have to defend the decision. Sometimes I've done that and then turned around and realized I'd committed myself to an unworkable vision of the story, but even that can be good, if it encourages you to ditch a bad path and pick a good one.
Most pitches-on-one-leg involve choosing specific, pungent details about your story that make it stand out. My friend Steven Savage has a knack for this kind of elevator-pitch summary: "A sorceress, an engineer, and a priest on a planet-hopping road trip with the owner of a mysterious collection of holy books." But the important thing to remember is that the pitch is derived from the work; the work is not molded to the pitch. If you pitch it one way and then realize you have to tell a different story, fix the story and change the pitch to match. You can always find a good, new way to sum it up.
* It's not very good code. Yet. But I'm working on that.