Mechanical rules are never a substitute for clarity of thought.

Don't document bad code - rewrite it.

An effective way to test code is to exercise it at its natural boundaries

Believe the terrain, not the map

Some compilers allow a check during execution that subscripts do not exceed array dimensions. This is a help, but not sufficient. First, many programmers do not use such compilers because They're not efficient. (Presumably, this means that it is vital to get the wrong answers quickly.)

Trivia rarely affect efficiency. Are all the machinations worth it, when their primary effect is to make the code less readable?

As we said in the preface to the first edition, C "wears well as one's experience with it grows." With a decade more experience, we still feel that way.