My entire productivity system is a checklist in a pocket-sized notebook. When I get to work, I write down the things I need to do, have been asked to do, and want to do (in that order) — most days it's 3–5 things. Each item is a specific task that I know how to do. This system, if you can even call it that, works for me for two reasons: 1) It gets the thoughts out of my head, so I don't have a constant "background no…
So I have a strict policy these days of only taking notes either on a piece of paper that sits on my desk, or in electronic form synced to all my devices (using OneNote fwiw but document files in Google Drive would probably work just as well).
I also have around 20 notebooks scattered around the house, office, car, friends's houses, etc.