C is a razor-sharp tool, with which one can create an elegant and efficient program or a bloody mess.

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

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.

Don't document bad code - rewrite it.

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

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.)

Mechanical rules are never a substitute for clarity of thought.