Types of chess "rules"

As I am reading about chess, I come across many types of advice and information that are called "rules". Here I have classified them into 5 groups. I would like to hear your opinion about this classification and some examples of "rules" that do or do not fit into this classification.

1. Rules of the game. What FIDE calls the Laws of Chess. These are the rules that govern how the pieces move and capture, how castling is performed, pawn promotion, etc. These rules are the same for OTB, correspondence or blitz chess.

2. Tournament rules. These would be rules that govern how pairings are done, the use of the clock, notation requirements, claiming draws, etc. These rules differ according to the type of competition. Correspondence rules differ from OTB and blitz.

3. Rules of strategy. What I am thinking here would be the fundamental rules that guide decisions of strategy. This would include the relative value of the pieces, the advantage of two bishops in an open position, rooks behind passed pawns in the endgame. Rules in this category would be expected to have few exceptions. If they had zero exceptions, and could be assumed to be true without further proof, we would call them axioms. Can anybody give an example of an axiom of chess strategy?

4. Rules of thumb. These would be rules that have so many exceptions that they must be considered only as rough guidelines. Knights before bishops is a good example. Some in this category might be called parables: for example the story of the man who left his inheritance on the condition that his son never captured a b-pawn with his queen.

5. Rules about how to think. Not specifically about strategy, but more about how to manage your own thought processes. Kotov's tree of analysis for example. Or the advice: If you see a good move, look for a better one.

Have I missed any categories of rules? Do you have examples that do not fit into these categories? What are your favorite rules?