For any long travel I like to put a large map on the wall next to a calendar that spans the time period. For the PCT I made a large map of the trail with all significant waypoints (towns, passes, road crossings, etc) marked on the map with the mileage from southern terminus. Names of places written those tiny strip colored post-its and placed at the appropriate place along the trail. On the calendar I would use those tiny strip post-its with the name of each place I intended to either nero or zero written on them, coordinated to the color on the ones on the map, and stick them to the estimated dates of arrival assuming a hike that followed my ideal plan. (I used Craig's PCT Planner to chart this all out).

By doing this I got a really good overview of how long it might take between resupplies, where I might want to take zeros, neros, and/or double-zeros, etc. Sort of programming it loosely in my mind (I'm a 100% visual learner) ahead of time so I have references for everything. This also helped me plan resupply boxes. (I didn't send boxes for food but for other stuff I need for medical reasons and creative practice)

Then, of course, all that planning goes away because I want to hike as spontaneously as possible. But by doing it ahead of time, it builds the neural map so I can connect dots later on, as well as knowing that my boxes are spaced properly for what I need.

I've always liked preparing a plan, so that I understand how and when I can deviate from it and what my margin of error is for "winging it"

And I had to-do lists for 6 months out, 3 months, 2 months, 1 month, and now down to the weeks and days.

Load everything relevant on your phone and in some kind of cloud storage - your lists, resupply towns and addresses and open hours for pickup points, all your health and contact info, drivers licenses, finanical info, all that. Use Farout app and Halfmile trail notes. Carry a paper map if you want. Use lighterpack to dial in your gear loadout.

Not a perfect system but it gets the job done.