Usually an idea comes up in the back of my head... Then i wait. After some time, the idea comes again. Now ill think about it, when i lay in bed, when im in a train, everywhere. Ill think about the technical implementation. How ill present it to someone else. To my boss. To my little brother. I think about the counterarguments, ill simulate discussions in my head, how ill defend it.

And then, one day, while thinking about it, ill start writing it.

Edit: Its like my brain needs enough entropy to do something. Then it works, then it generates entropy again, eg youtube, gaming, working on something else, dreaming etc