This is a subject I’ve spoken of a few times in the past, but I think it needs to be looked at with an eye to why we are doing what we do in the design cycle.
So we can start either from the top down or from the bottom up. In the top down, we have a real idea of what kind of world we want, maybe some of the cultures, we may in fact have a particular story we want to tell. So we work on building the underlying details to support that story. On the other hand, if the story is about a ship that has just found a planet orbiting at some random point within the habitable zone of a particular star, we might want to build up from the more basic astronomical stats and flesh-in the planet its life forms and cultures and see what stories that fleshing-in might provide us with. Or maybe we just want to experiment; play with what effects more extreme astronomical conditions might have on life and anthropology(or whatever the xenological equivalent of that might be).
In any case, it’s important to remember that this is a cycle, or more likely an oscillation.
We might start a bottom-up procedure only to find that our astronomical conditions were too extreme. Perhaps at some stage in the process it turned out to be implausible that you might have a sufficiently complex culture, or life… or even a planet. You’ll need to backtrack a bit to try to make the situation more believable. Or maybe a story suggested itself to you as you were building the world and now your backtracking to fit the story.
We might start a top-down procedure. We have some sort of a story and we want to fit the world to it. As we build downward, cultures and life-forms and geography are built to support the story. But perhaps they also suggest additions to the story. This may require changes to propagate back up through the overlying strata of life and history and plot. Or maybe you just change the story a bit and propagate changes down to fit.
At every stage, whether you’re building upward or downward, there are spreading forks of possibility. You only need to use your imagination to grasp them.
No matter how technical you want to be with your world-building, and I’m still gunning to be very technical, indeed, it is important to keep your imagination ever open. You need not only to follow the technical steps like an automaton, but be ever ready to see and follow the roads that those steps open to you.
This has been my failure of late. I have been focussing too tightly on the rote technical steps and failing to follow the flights of fancy, the new vistas opened to me by an entire world with which I can do as I like. This has not only bored me but it has stifled my creativity, made it harder to write and at the same time harder to read.
Whatever you start with, be it the basis of a story or just an astronomical caprice you want to follow, remember that start is not sacred. Great artists paint over their mistakes. If you feel that the development of your world has made your original story idea implausible(while providing more interesting story ideas), change the story. If you can’t fit the world to your story, and the world doesn’t provide comparably interesting ideas change the world.
If the world and the story both hold your interest, fork the project. Build a new world that will better support the story and save the world you’ve been working on for another story, one built off of that world. Or reverse that order. Whatever. The important thing to the design cycle is an eagerness to follow your imagination, and a willingness to go back and change things when they begin to constrict the story.
I hope that I was of help,