When you have your characters moving through a house, you have to have some sort of a floor-plan of that house in your mind. Otherwise, they wil move through one hose in chapter 3 and another house in chapter 8.
It wasn't until I was writing _Heart Ball_ that I realized that I was always using the same floor-plan. Usually, that doesn't matter; if the house is really important, what makes it important generates another floor plan.
In _Heart Ball_, though, the f-lead babysits; that takes her into numerous houses. They can't plausibly all have the same design.
Where this leads back to the subject of the post is that I have *never* set this plan to paper. It's entirely, and indelibly, in my mind.
On the other hand, I start a story by opening a folder, copying in a blank Word document and a blank notepad file, and then open a Notepad file called "Names."
That's where I keep the names of the protagonists, their relations and co-workers, and the other characters.
Even so, Denny caught my switching names of the (maybe) 4th most important character in the long story to start next.
I keep a floor plan in my head forever; I can't keep the names of the characters straight.
Actually, the names are the things about the characters I have the most trouble keeping straight; I can hear their voices; I know what they'd never do.
The Brennan story running now involves 6 major characters; two of them have been featured in 25 previous stories, several hundred thousand words. The others come in and out or grow up. I almost never go back to see how the character would react.
(One thing I have put in lists -- none available to me now -- is the words each character would use for what might be called "sex things." Penis, cock, rod; breast, boob, tit; condom, rubber, contraceptive.)
So, what do you remember easily, and what do you need to write down?