Cool idea! My methods change a lot, but like Sparrowhawke, I often pick a couple of my favorite tropes and see where they fit in.
I also often pick a time period and an area, or a specific aesthetic I want to write. That sounds vague because it is. I have no idea what I’m doing most of the time and I definitely can’t put it into words. LOL
Like, one of the books I’m planning has a very specific aesthetic that involves lighthouses and masquerade balls and the colors red and navy and violins and *vague gesturing* yaknow, that. I wish I had a plot instead, but I just get a vague, uncertain idea XD
Scrolling through mood boards on Pinterest does give me character ideas pretty often though!
Without darkness, there is no light. If there was no nighttime, would the stars be as bright?