1 – Start with the kind of story you want to tell, the mood of it, the point of it, then shape all the things that make up a world – the geography, the economies, the cultures, the politics, the religions, the peoples, the flora and fauna – so that they reinforce the story.
2 – Remember that world is slave to the story, and not the other way around.
Why to do it?
I’m not so sure.
I have a world. It’s called Ehre. A few years ago I spent an incredible amount of time and energy building it from the ground up. I bought a program called Fractal Terrain Pro so that I could make a realistic globe, with rivers and mountain ranges that made geological sense, and from the simulations it created drew world maps and named countries and cities and peoples. I invented seven thousand years of history, the pantheons of several different religions, a system of magic, numerous forms of government, a number of currencies, the naming conventions of half a dozen cultures, some social hierarchies, a few different slangs and cants, the rules for a gambling game, and a detailed map of the city in which I intended most of my stories to take place.
I did all this because I only wanted to do it once. I figured, if I was going to write fantasy, I would set all my fantasy novels in the same world so that I wouldn’t have to reinvent the wheel every time I started a new book. That would be the smart, efficient thing to do.
Anyway, like always happens with this sort of thing, I ran out of steam after about half a year, and decided I would use what I had to write a novel set in my shiny new world.
I had a lot of fun writing that novel, lacing it with all the lore and culture that I had spent so much time and effort creating, and I was very pleased with the end result. Unfortunately nobody else was. It got turned down by two big publishers, and my regular readers had their reservations as well. Everybody hated my main character. That’s all they ever talked about. They didn’t take any notice of all the effort I put into creating the world.
Cut to last year. I sold Jane Carver of Waar, my ten year old first novel, to Night Shade Books.
When I wrote Jane I literally made the world up as I went along. If I needed a god or a monster for the next scene, I’d come up with one on the spot. If I needed a town, or a race, or some little detail to bring a scene to life, I wrote it on the fly. In fact I still did that as wrote the second book. For instance, there are Seven Gods on Waar, but I’ve only bothered naming two of them – the ones I needed for the plot. The rest are still a mystery to me.
Nobody who’s read Jane has ever commented on how little effort I put into creating the world, but everybody loves Jane. That’s all they ever talk about.
So, by all means, build worlds if you like to. I had a blast doing it, but remember that, no matter how often people pin the map of middle earth to their wall – like I did when I was a kid – they wouldn’t have fallen in love with that world if they hadn’t liked Frodo and Bilbo enough to follow them through it.