Technical design document

Depends do I expect others to be part of it at some point or not. I don't do too much technical design documents just for myself. I do a lot of diagrams though, and rough sketches, but not full blown documents. But if I plan / anticipate that there will be others also taking part in development (be them technical or non-technical people), I usually do for all features tech design documents as well. Creating technical design document helps me "naming" things, and creating unified language how certain features and processes are called. It is then easier to explain to other people, and document makes it (ideally) crystal clear for them what everything is called. And it has huge impact when collaborating with others.

I usually write some highlights (the goals, data flow diagrams, architectures) for each development escalation.