I don't do all the background and the worldbuilding before I start the story. What I do is I work out the bare minimum I need to start the story, and often that really is a bare minimum - it's a character in a situation, and I know nothing about the character, I know nothing about the situation, and then I think about it for a long time, and make notes about where I think the story is going to go and so on, but I don't really make notes to do with the background or the magic system or the world.
Garth NixWhen the dead do walk seek water's run, for this the Dead will always shun. Swift river's best or broadest lake to ward the dead and have and make. If water fails thee, fire's thy friend, if neither guards it will be thy end.
Garth NixSam picked up his pack, but before he could put it on, Mogget leaped onto it and slid under the top flap. All that could be seen of him were his green eyes and one white-furred ear. "Remember I advised against this way," he instructed. "Wake me when whatever terrible thing is a about to happen happens, or if it appears I might get wet.
Garth Nix