Ok, exactly as described in 22.08 in the workbook, I just started a big new thing (new job! 
). The advice there is fairly brief:
"I recommend following this guide. But rather than it being one large process that takes many weeks, make it lots of small processes that you do more frequently.
“You might set aside a few hours every Monday morning to think about what happened last week. Use all of the techniques in this guide but do them more quickly, more often.”
I wondered if anyone has built a system this way already and has more detailed/specific advice based on their experiences?
Kind of? My main system (for my current education) went through several iterations, but none of them stuck until I built one based off of experience.
Story
I didn’t exactly put aside time each week to think about how my stuff was organized, but I always had the thought of “how would I JD this” in the back of my head. I had soft-built a JD system a few months before starting, but I didn’t use it as it was completely useless for the reality of managing a college education. I simply had no idea what to expect before I actually got in it. When I sat down after a year and decided to try again, I had the experience to know and understand what needed organizing and how different things fit together.
A problem I ran into however is that I was relying on memory for anything that didn’t have a computer file associated with it (I didn’t have the workbook and it’s advice to write down everything). There were several things I missed, in fact I didn’t think to add what is now my largest category (a general “friends, clubs, and fun” category) at the start. If I had the notes, I would have added it while designing.
Practical advice
Make the discovery process a part of your flow so you don’t forget it.
Consider an immediate approach: Any time you create a new document, immediately create a sticky note (or equivalent) of it to track later. Take notes immediately after a meeting. Maybe set aside a few minutes on Fridays (or end-of-week equivalent) to catch anything you missed during the week. This way you catch everything as soon as possible.
Or maybe writing things down immediately doesn’t work for you, and you’d rather do a weekly “what did I interact with?” review. Or daily. Just make sure it’s not so far apart that you have a chance to forget things!
The point
Write it all down, anything in scope is fair game. Be serious and strict about it: if you interact with it, write it down. Do not rely on your memory!
You’ll have to find a process that works for you, and be sure not to rush this. Take your time, even a year if you need to, and be intentional about planning this system.
Good luck!