Avoid pronouns like “it” and “this” when they can refer to multiple things.

Describe a function’s behavior with as much precision as is practical.

Illustrate your comments with carefully chosen input/output examples.

State the high-level intent of your code, rather than the obvious details.

Use inline comments (e.g., Function(/* arg = */ ... ) ) to explain mysterious function arguments.

Keep your comments brief by using words that pack a lot of meaning.