Worlds

In whatever you write, you have to write in a world.  Rules and laws of physics may be different than the one you live in like Alice In Wonderland.

In Avatar you see lots of different wildlife and plant life that are similar but different than the real world.  Making a world different makes the reader want to explore.  A world could be historical or futuristic.  It could be malicious or heaven.  It could be as small as a grain of pollen or as large as a universe.

Whatever it is, the world encompasses the traits of a character.  It will either challenge or help your hero.  The Matrix, Lord of the Rings, Alice in Wonderland, Planet of the Apes and Aliens all had malicious worlds.  The heroes had to explore and survive the worlds they were in.  They were also extremely fictitious worlds.  Meaning that they were environments we would not recognize just looking at he world we live in.

Sometimes you do want a world based on this current world we all live in.  Stargate SG-1, Sanctuary For All, Superman, Batman, Ironman...etc all took the real world and altered it slightly by adding creatures, characters and sometimes things that just defy the laws of physics.

I think defining your world first could prove to be invaluable to bring your piece of literature into a consistent and visual experience.  It could take a second, or several weeks to accomplish this.