practice makes perfict

The homophone for "practice" is "practise". Both spellings are correct, but "practice" is more common in American English, while "practise" is more common in British English.

Common intruder practices are Spoofing and Sniffing.

A common belief or practice which may or may not be true or have practical value could be called a tradition or a custom.

is based on custom and common practice, on court rulings in specific instance, or on the ideas implied in those rulings.