Going to talk world-building, and I’m going to do it with a little help from Croidure, who’s been running games in a homebrew world for a decade or more. Croidure’s take on world-building is a little different than mine; I’m more of a ‘throw it at the wall until it sticks’ world-builder, she’s a little more methodical. But both methods work; we both aim for the same thing; a consistent, living world with its own quirks and rules.
I’m going to start with the old author’s saw; be willing to kill your darlings. If something doesn’t fit with the system you’re using, toss it. If something doesn’t fit with the narrative, shelve it. If you love it? Kill it as many times as you have to.
Now. Normal advice is ‘start small, start with a village, or a town.’ Croidure’s advice goes the other way; literally create your world; its stars and continents, its sun and moon (or moons). I’m inclined to agree; you can do it the other way, and it will work, but this is good for consistency, and consistency is going to be your good friend when you’re ready to turn your friends loose in this new world. By all means, start them in a small town or village, but make sure you have a good idea how the rest of the world is laid out in enough detail to be able to say, ‘well, this is likely to happen if you do that ..’ in one form or another. Don’t just hurl something random at them; you’ll have to explain it later, and that rarely ends well.
Donjon has a fractal world generator that looks like a good place to start. Building a water world? A giant desert? Something in-between? Play with it until you have something that works for what you want to do. Or until you get an idea from the results. Look at what you have. Where are the major cities? What are the major trade routes? Where is the farmland? Where might the threats come from, and why?
If you want your sun and stars to be a little different from standard, this might be a useful device for the purpose. I haven’t had much chance to play with it myself, but I’m definitely intrigued by the possibilities. Remember that your moons and other large celestial bodies will effect your tides; more than one moon will make for some very interesting oceans. Deities and religions are frequently based on those stars, and celestial bodies have been used by more than one culture to predict or explain a hundred odd occurrences, as well as a navigation aide.
So. You have your world, your stars. You can then figure out things like deities, pantheons, magic levels. That last is important; you need to know what’s available, what it can do, and who can use it other than the PCs. Generally assume that anything your players can find, they will use, and anything your NPCs have access to, your players will also have access to eventually; it keeps power levels consistent over the long term. Also consider possible consequences; for example, magic can be as much of a danger as a help in some worlds. Elemental magic in Mallire is a matter of will, imagine a thing, make it happen. But using it too much, or casting too powerful of a spell draws the attention of chaos. Chaos twists and devours all in its path, and powerful elemental mages are tools it wants, tools it needs. Rune-magic binds and constrains chaos, but can be eroded by it.
It took /months/ to come up with that, and I don’t think I’m done with it.
Now that you have your big picture, start looking at what inhabits this world, where it lives and why. Fauna, flora. Sapient races. Who lives there? Where’d they come from? Why do they do what they do? What customs have spawned from their living traditions? Are they /really/ so different?
Croidure dug a little deeper than I would have while she was doing that, she went all the way into real-world biology; you can take a look at her take on races, and animal biology here.
You can use real-world animals and examples. You might alter them slightly; if you want lava-dwelling fish, you have to consider how they would survive the heat of molten rock; and for that matter, why and how the rock stays molten in the first place. If you want flying whales … you have to have an explanation; you can’t just say ‘a wizard did it’ to everything, that gets old very quickly, unless a mad wizard really /did/ do it, and … you could probably build a whole quest around that particular trope.
When I started building Mallire, I first decided I was going to limit the major races to eight; linked to the elements, and I went from there; more than just my notes on building races can be found here, but this is the post on the sapient races; most of them aren’t so different in their way. Some are very different and by now, many have had their names changed, because … well, it’s a work in progress, because these things are. You find a thing doesn’t work, you change it. These things happen.
Where your people are human, or human-like, are they like us? What kind of world do they exist in? Is it pseudo-medieval? Is it far-future? Is it somewhere in-between? How are they governed? What laws have they made? What’s the life of an ordinary citizen like? If you have a sapient race that isn’t humanoid, where did it come from? Does it co-exist with humans? Do they recognize it as sapient, or have they been, as a group of humans sharing a hostile garden world with a race of sapient predators might, have they been eating each other, neither recognizing the other as sapient?*
How many of these questions can you answer? Or, perhaps, how many of these; Croidure makes heavy use of this checklist and I would be willing to bet there are others. Probably several, but this is the one I was given a link to.
*I should note that the example I used above exists in my world-folder, I generally keep it for low-magic or science fiction settings, and haven’t had a chance to fish it out in a game.
At this point, you have the bones; you have the world, and the system it spins in. You have deities and people and if you want it, you have magic. You have animals mundane and/or magical. You’ve figured out the laws and what sorts of things get attention, positive and negative. Are you done? Probably not; a world doesn’t build itself, and turning a group loose in your world is supposed to help flesh it out. Let them explore. Let them find things, if necessary, let them break things. Show them your world; don’t just tell them about it. Let their characters live in it.
In closing, I want to know how you build worlds. Moreover, I’m fairly sure I’m not the only one curious; so, please. Share! Feel free to comment here, or even on the Portal Forums, or on FB. Tell us about your worlds, your peoples. Tell us about the hitches and hiccups, what worked and what didn’t.