I usually start with a character I want to play the game, sometimes it’s the character at the start if the game, sometimes it’s the character at the end of the game.
Once I have that one end of the character arch, I figure out other end so I have the story bookended.
After that, it’s pretty straight forward, the ending tells me how many rounds they have to win/lose for the story and what changes I need to make during the rounds.
For the rounds themselves I start with the change I’m making, grab a change from a previous story and then fill in the missing ones with some new ideas. And by ideas I mean something that sounds interesting as I usually don’t know the details of the unused changes myself 🙂
If I use one of those changes in a future story, I have to make up the details then.
Once I have that all written down in a quick chart of the rounds, I start writing the actual story, using the chart as I move through the rounds, because it’s super easy to get out of sequence mess up how many cases have been opened and which ones are cash and bimbo cases 😉
I don’t keep any ideas for changes per say, but I do keep a list of ideas for characters and stories.
I’m taking some vacation in a few weeks and I’m hoping to do some writing, including at least one BoB story idea I’ve had around for quite a while.
Hope that answers your question.