One of the things that is a useful technique for level designers is storyboarding (http://en.wikipedia.org/wiki/Storyboard).
The writer gives us an outline of the story, and we make levels to fit it.
That's the theory, anyway. In reality, it's a bit more complicated. The steps between turning the writer's vision into actual concrete levels are long and tough, and quite often, the resulting levels don't always reflect perfectly what the writer had in mind.
The writer has a vision on his head and he translates it into words for the level designers, and often the visual element doesn't translate perfectly; like someone once said, "writing about music is like dancing about architecture". The same principle holds true in respect to putting a vision into words. Often, much can be lost in translation.
One of the tools used to help fix that problem is the story board. More or less, it's a simple scene-by-scene visual representation of the story. This allows the writer to look at what we're going to be designing and give us feedback as to whether what we have in mind is what he had in mind.
It may sound simple or silly, because one would often think 'well, can't he just *tell* you what he wants?'. The truth of the matter is that yes, he can tell us what he wants, but he is putting a vision into words, and the original is always better than the translation. Story boards allow for a better translation, as it were.
And a better translation lets us level designers do a better job, which, in the end means that you, the player, get a cooler game ;)
