Fantasy writers have a lot to keep up with, as they are faced with creating a believable world. Using a layered approach can make their job a lot easier.
When writers sit down to create novels, they will be beset by as many obstacles as the characters. Fantasy writers often find themselves with more problems than novelists of other types, because they have to do more than simply put down characters in a convincing way: They have to invent entire worlds. This gives them a lot to keep up with. Therefore, the best approach is a layered one. Figure out the basics first, and then work from there.
One of the first things with which a fantasy author will have to contend is terrain. What sort of world is he writing in – physically? World type will actually help determine how much detailed terrain information he needs to give. If he is writing about a type of world his audience has little or no experience with, then he may need to give more information. For example, if he is writing about a wilderness from long-ago, as opposed to an urban, contemporary setting, he will have to familiarize the reader with this type of world, unless his readers happen to be lumberjacks.
Another important element of world-building is culture, including the overall world culture and that of the groups within that world. In fact, it is a good idea to make culture the very first consideration, since that may determine what type of terrain will best help tell the story. According to Stephanie Cottrell Bryant at
Magical World Builder's Guide (http://www.web-writer.net/fantasy/#basic), creating a convincing culture is also a good way to keep character names from sounding silly.
Since it is such a basic fantasy element, the author will have to make a decision about magic. How much is there? Who uses it? What are the rules governing it? How does everyone feel about it? The more detailed questions may actually answer themselves once the author decides if the world is high-magic, low-magic or somewhere in between, and figures out the general culture. For example, in a culture where magic-users have set themselves up as a ruling class, non-magic-users may resent or fear magic, if they even know or believe that magic exists.
Although there is much more to writing a fantasy novel than this, answering questions about these three fantasy elements will help the author set the foundation for their world-building exercises. As long as he keeps the rules of his world consistent, and his details relevant, the world he creates will be a convincing one.