Martin Scorsese once said cinema was about what’s in the frame and what’s out of it. Storytelling, and worldbuilding, are the same way: what you leave out is as important as what you keep in.

Many people assume the editing process is confined to the story itself—that the world is like a darkened room, and the story is like the flashlight you shine around that room to illuminate it selectively. This is true, and it’s a useful analogy when you’re actually writing the story.

But I’ve noticed that few people seem to think the worldbuilding process involves its own selectivity as well. They assume it’s an all-inclusive process—that you have to cover every detail, paper over every crack and spackle down every hole or your world will be somehow incomplete.

Well, what’s complete? What’s incomplete?

At a couple of conventions in the past I’ve participated in roundtable workshop sessions for storytelling. I’d sit with a few other folks, and we’d start by going around the table and asking people to talk about what they were working on. In more than a few cases the project in question was some massive piece of work spanning generations and continents, with maps and family trees already sketched out to go into the endpapers when the book went to press.

I had to admire the ambition that went into all that. Who wouldn’t? Here were people, some of whom were barely half my age, throwing themselves into stories of such scope as to daunt hardened professionals. They were not afraid to dream big, think bigger, and write even bigger.

But is ambition the only thing? Well, it’s a good place to start, certainly. Still, after that initial burst of creativity, that first surge where you start cataloging the name of every species of fauna and labeling every tributary of every river, there are two major problems that can surface:

a) The worldbuilding eclipses the storytelling. In short, the process of building the world becomes an end in itself, and the storytelling falls by the wayside.

b) The worldbuilding itself dries up, and the project along with it. The sheer level of detail you’ve confronted yourself with becomes forbidding. It becomes harder to maintain that level of interest in it, and the whole thing stalls out.

Both of these are rough on a writer. What I suspect, though, is that things like this stem at least in part from some misconception about what worldbuilding is all about.

When you build your world, you’re making to some degree a statement about the kind of story you’re going to tell. If you’re telling a story that revolves mainly around, say, economics, it makes sense to go into a fair amount of detail about the use of money in your world (as was the case with, for instance, Spice and Wolf). If economics is just another world detail, then you don’t need to chase your tail with details upon details about whose faces show up on what minting of each coin. You can talk about the basic units of money used in your world, and maybe the level of financial sophistication involved (credit? financial markets? futures?), but anything more than that is likely to lead you away from your story rather than back to it.

In fact, there’s a handy metaphor for you: Worldbuilding is making the road that leads most directly into your story. Every piece of background you come up with should be, as directly as possible, about something in the story itself.

The elements of your story’s background that you choose to expand on and add detail to are things that the story needs most directly to flourish. Sometimes this can sneak up on you without you even realizing it, but the easiest rule of thumb to apply is Do I spend more time on the story or on the world?

There is something to be said for the influences of things you never actually see firsthand. Fabled movie director Erich von Stroheim was said to have ordered the creation of hundreds of pairs of underwear to be worn by many extras in one of his films. He believed this would help create the proper state of mind in his actors, even if the items in question never once showed up on screen. And Oliver Stone maintained a rowdy, shredded-nerve feeling on the set of Natural Born Killers by playing loud music and firing guns loaded with blanks between takes. And who’s to say your musical playlists, art commissions and other creative accoutrements for your story aren’t useful?

I’m not against any of that stuff—in fact, it would be hard for me to come out against any of it, since I have playlists for my own stories and am considering art commissions for character illustrations myself. But I don’t let any of that stand in the way of the work that needs to be done. The story still has to be written, and the world that I’m building must be built in such a way that it makes the story easier to write by showing me what’s most crucial, not harder to write by swamping me with too many false details.

Someday, when you’re rich and famous, you can take that wiki you created which describes the number of pieces of every suit of armor worn by every country’s soldiers, and post that up for all to see and pore over. But for now, there’s a story to be told. Build the parts of your world that are most needed by your story first.