Here’s my approach to documentation. It’s about habits as much as it’s about actually writing anything down:

1. Never setup anything important via naked terminal commands that you will forget you did

2. Always wrap important commands in some kind of “setup-xyz.sh” script and then run that script to see if your install worked.

3. If you need to make a change to your service, ensure you update your script and so it can be re-run without braking anything

Get into the habit of this and you are documenting as you go