Please state in which country your phrase tends to be used, what the phrase is, and what it should be.
Example:
In America, recently came across “back-petal”, instead of back-pedal. Also, still hearing “for all intensive purposes” instead of “for all intents and purposes”.
My favorite of these mnemonics (try spelling that from memory) for these arbitrary distinctions was in a movie that had some evil lords in it. The father way telling the son,
“Pheasants are hung, peasants are hanged.”