Way too often, people focus only on achieving the goal, forgetting that the machine is as important as the goal itself. In order to achieve your goal, you need a well-working machine. And you can get it only by training and testing it.
The purposes are:
To move you closer to your goal.
To train and test your machine (i.e., your people and your design).
Most people focus on the first one only, which is a mistake.
Everything is a case study.
If you look from this perspective, you can define what case it is and what principles you can apply.
When a problem occurs, discuss the machine and what to do about it.
Be aware of micromanaging.
When making rules, explain the principles behind them.
If you want your people to hold others accountable, you need principles that are sound and that have been tested through open discussion.
Your policies should be natural extensions of your principles.
The policies are very important because they will drive individual decisions. Basing them on principles will ensure that they are consistent.