My number one rule for good code: the one that make it very clear and explicit what are the business rules. The code should talk to you no different than a PM.
My number one rule for good code architecture: the one that reveals clearly its intention. The architecture of a house reveals clearly the owner’s intention. You don’t need to ask the architect.
My number one rule for a good code review: the one that focus on code specification. Is the code doing what it is supposed to do?
My number one rule for a good suit of unit tests: the one that checks if the code solves the problem, not if the code can run.
I’ll do a follow up on what I think is the number one mistake on each one of these topics.