As I said in the previous chapter, the inspiration for this one came from a rant from the movie Revolver.
I used to refer to this principle as "What's in it for me" because of this inspiration but Cui Bono is a much better way.
The point is simple, in any situation, invest yourself into understanding the complete map of all actors' "what's in it for me". Or in other words, cui bono - to whom is it a benefit.
You have to accept with a kind mind that most situations are crafted in a way to control the balance to some advantage. If you want to reject this principle, it's fine, move on to the next chapter. I know life has its way to teach this lesson on its own.
Once you have accepted that, you can start to look at it with an open mind.
Whether it is a salary negotiation, a promotion, a technical decision, a team restructure or the provider of the paper in the printer -> cui bono.
The open mind is very important. You're not approaching this like a witch hunt (or a paranoid conspiracist mind). People just doing things because it came to them is a valid and common answer. As in, it benefits them because that's an easy choice. Don't default to find conspiracies at every corner.
I was promoted in the past because it benefited my manager. I promoted people because it benefited me. In both cases, there was a lot more benefits to a lot more individuals direct and indirect. Understanding this empowers you to make better decisions. Just like Ray Liotta said in Revolver: "The more the man invest in that question, the more powerful the man becomes".