I'm always in the preparation mode for fiction, because there are always stories. You just have to look around. Observation is the crucial ingredient. But making a mental note of a character quirk is not writing fiction. And coming up with a apt description of behavior or appearance isn't writing fiction either. On the other hand, those mental notes can come forward the next time the fingers are poised over the keyboard. In the end, I can gather all I want. I can mull over thoughts, and I can garner real tidbits from people around me. The preparation time for fiction includes all types and sorts of preparation but has to include keyboard time. Simply put, as an long ago writing mentor used to say, something has to happen.