Depends on the day, really, but I usually do some combination of the following. (I mostly write non-fiction.)
- Read a bunch of different books
- Take notes as I’m writing, writing down any thoughts I have or anything that captures my interest (I do this for both fiction and non-fiction)
- Look back over my notes every now and then, looking for recurring themes or interesting links
- Schedule some time for writing and, when I sit down, copy a random note into a doc
- Add any relevant notes and move things around until I have the basic skeleton of something
Basically, I do a bunch of little things too, (a), stoke my curiosity and, (b), do as much as possible before I need to write anything.
I’m also a copywriter by trade and I do similar things when I’m stuck on a project. They mostly boil down to “If I can’t think of one idea, think of 20.” It’s much easier to aim for volume instead of quality (and edit for quality later).