Whatever your system, be consistent and keep the records in a safe place. I use my computer, create a Word document titled ST1300 Log, and begin the first page by listing the obvious maintenance parts with numbers and costs. Things like oil filter brands w/ numbers, push pin numbers, etc. This is for MY benefit - its easier than looking in the Shop Manual.
Then I begin a line with the Date, Mileage, who did the service, approx cost. Next few lines are individual service items.
For example:
Nov. 12, 2019 43,200 Self $50.00
Changed brake fluid
Changed front pads, cleaned pistons, lubed pins
Changed oil+ filter
Bled clutch - new fluid
Installed speedo healer ($129)
This is as much for me as it is for the next owner, and I can look back and tell exactly when the last tire/brake whatever service happened.