I like to work on one novel at a time, as I have found that not only is my focus much better that way, it serves as good motivation to actually finish the story before moving on to the next — otherwise I’d have a million works-in-progress and no endings.
Inspiration, on the other hand, doesn’t follow my schedule. It strikes whenever it pleases. That’s one of the reasons why I prefer keeping a handwritten binder rather than typing on a laptop. My binder is indispensable, always nearby, and never low on battery.
Whenever a new idea hits me, I write a page or two like this:
It’s not beautiful or elegant. In and of itself, it’s too vague to be particularly enjoyable for reading, but it contains everything I need to remember the idea.
Sometimes I don’t know any names, so I write down variables instead, such as “B” or “Z”. Those pages tend to look really weird.
Then it goes into the back of my binder, and waits for its turn. The proximity ensures that I often see it and thus never forget its existence.
When it’s time to start a new novel, I pick the idea that has the loudest voice.