Having previously explored how the GM can best tackle the roles of judge, storyteller, and adversary, in my last column I introduced the role of world-builder, and discussed the need to choose your genre and rules setting before you start building your world.
Now we come to actual world-building. And when it comes to world-building, there are two major schools of design that you need to know about: "top down" and "bottom up." Proponents of "top down" design are world-focused. They like to establish a framework for their world, laying out the backstory, major characters, and points of interest in advance. The player characters, when they are created, are made to fit the world. In this way, the gamemaster achieves a holistic creation, in which each part makes sense in the context of the whole.
Proponents of "bottom up" design are player-focused. They begin with whatever will be in the immediate vicinity of the player characters, and flesh that area out in great detail. They generally leave the framework of their world open, or at most very thinly sketched, feeling that major characters and points of interest can best be developed over the course of play. Often he will create sections of the world as needed to fit the needs of the player characters, or even let them be created by the players themselves. In this way, the gamemaster builds an open setting that is shaped to the needs and tastes of the players as they evolve in play.
Many early campaigns in the hobby began with bottom-up design. Gary Gygax's famous Greyhawk setting, for 1st edition Dungeons & Dragons, was a bottom-up design. Greyhawk began with a town (the city of Greyhawk), with a nearby dungeon (the castle of a mad wizard). The rest of the setting was fleshed out over time in increasing detail. The same is true of Dave Arneson's Blackmoor and Ed Greenwood's Forgotten Realms. In contrast, many modern campaigns are designed from the top-down. Dark Sun, Eberron, and Dragonlance, for instance, were all campaigns that began with a framework and backstory, and both Cyberpunk 2020 and Shadowrun 1st edition were entirely top down, providing extensive details about the world and backstory, but a scant few pages on the actual micro-settings of the campaign.
Which is better largely depends on your personal preferences, but there are some tonal factors to consider. Top-down design lends itself to high fantasy, in which the scope of the adventures is potentially epic. Bottom-up design lends itself to swords-and-sorcery, in which the adventures are of a more personal scope, and what matters most is the characters, not the world. Top-down design tends to result in a world that is flavored and thematic, but less flexible. If you don't write in a place for minotaurs into your top-down setting initially, they are very hard to add later. In contrast, bottom-up design worlds tend to be much more gonzo: Aztecs rub shoulders with Romans, and things tend to get added that don't fit into any larger pattern, because there isn't any. It's Frodo's Middle Earth v. Conan's Hyboria.
My personal design method falls in between the two schools. I call it "top down, zoom in". The "top-down, zoom-in" approach means starting with a light top-down framework, but creating increasing detail as you get closer to the areas of the setting that the players are most likely to interact with. Ideally, you end up with a setting that has much of the openness and playability as a bottom-up campaign, and much of the cohesiveness of a top-down setting.