At work we are using Confluence and GitHub.
What to put in Confluence and what to put in GitHub?
When to use GitHub wiki vs checked-in documentation?
How to deal with information vs knowledge?
How to avoid outdated documentation?
How do you make sure developers in your team or in the company do not change the public API of the application when it is not planned? Yes you can write unit-tests, but they can also change/fix the unit-tests to have a green build.
Let's say you have access to an automatic online factory that can manufacture reasonably anything, at the cost price, from a blueprint you upload. What will you build?