Back in the day I kept a fancy log book, like it would make a difference, LOL
Now I just jot down date, mileage and work done on swiped bank envelopes and stack 'em
in a box. I have gone thru them to back track a repair, etc, once in a while.
However, I printed off a chart on card-stock in landscape (sideways) to track
long term items like, the last time I did: - and the change intervals I chose
- bleed brakes
- lube tie rod ends
- change tranny filter
- scan for hidden OBDII codes
- replace spark plugs
- change coolant....etc.
So I use this single chart as a quick visual reference/ reminder for next service that is needed
over several years, etc, without forgetting. 1 card per car.
Back in the day I also made up job sheets for certain repairs where I had found tricks and trick tools
I might forget if not written down. After all, I had a lot of "stuff" to fix!