"people"
It's about the characters first, then I sort through the mess that is my story ideas. It's the characters, who tell me what genre the story is. What it's really about. How characters interact with each other. And what direction I should take. At least for stories.
Other forms of writing, have me thinking about what the reader's perspective might be. Whether I should be helping with useful information or evoking an emotion. Whether I succeed or not is a whole other matter.
So, I guess that still suites the one word answer.
Interesting question though.