Swarming and pinning
Sitting in front of a blank page (text document, diagram, whatever it is) is a great way to get stuck. For me, at least.
I mean, for trivial tasks it's OK to just start with a blank canvas and plow ahead. But when it's time to do deep thinking, I need previous, more chaotic phases of thinking first.
Significant projects start with a buzzing of thoughts; a swarm of vaguely interconnected ideas, a storm of possibilities. They come and go and are hard to picture as a group. They multiply and grow into a cloud that can be even overwhelming.
When that happens, it's time to start catching and pinning. Grab a piece of paper, jot some notes. Start creating categories, make lists, draft diagrams. One by one, put the swarm members on paper or discard them.
The result of this first exercise is not a neat document: it's a first pass attempt at making sense of the swarm. Some pins here and there and some dead bugs scatterred on paper.
Walk some more, let things vibrate. Iterate, refine, discard.
Once a good number of pins are in place and the collection has some structure, producing output becomes easy.