Another effective [debugging] technique is to explain your code to someone else. This will often cause you to explain the bug to yourself. Sometimes it takes no more than a few sentences, followed by an embarrassed "Never mind, I see what's wrong. Sorry to bother you." This works remarkably well; you can even use non-programmers as listeners. One university computer center kept a teddy bear near the help desk. Students with mysterious bugs were required to explain them to the bear before they could speak to a human counselor.

Don't document bad code - rewrite it.

Get the weirdnesses into the data where you can manipulate them easily, and the regularity into the code because regular code is a lot easier to work with

Each new user of a new system uncovers a new class of bugs.

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

Mechanical rules are never a substitute for clarity of thought.

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.)