So what is the purpose of world building? To some of you the answer may seem obvious, but many readers may not see the point when they could just sit down let the world unfold as they write. There is absolutely nothing wrong with that approach and it may work better for some writers. And no matter how much world building you do before sitting down to write a chapter or short story, world building will enviably occur in the process. Unanticipated details tend to surface in the process of writing.
However, doing the bulk of your world building prior to sitting down to write will free your writing. By figuring out a basic character profile before writing you will have a better feel for how that character will react in certain circumstances. Having names for places, characters and things can prevent stalls during the writing process that will distract you from the action.
I don’t want to mention any authors in particular but when an author writes a story set in a world that unfolds as they write, it tends to be quite obvious. Their worlds tend to feel claustrophobic and even inconsistent. The more work you do fleshing out your world the greater the scope and it will help you to avoid inconsistencies in your work.
I recommend setting aside time specifically for world building and separate time for writing. Should you find yourself needing to world building in the middle of writing, and it threatens to interrupt the flow of your writing, simply make a note of it and come back to it later.
Of course, another reason for world building is that it is satisfying in and of itself. Even if you do not plan to write (or GM) creating your own world can be incredibly rewarding. For many, the appeal of fantasy is being able to explore new worlds. With world building you explore the world by creating it. You allow you mind free reign to create something unique based upon your own interests and ideals. Much like writing you will also learn much about yourself and your understanding of the real world in the process.
Fantasy World Forge 