I find letting the kids create their own helps them memorize better than repeating ones taught over and over since they relate them to what they are familiar with or interested in. For example, for order of operations, the old acronym was "Please excuse my dear Aunt Sally". I had a student interested in going into medicine come up with "Please take me to the Emergency Room, so the Math Doctor can save Aunt Sarah" (for Parenthesis, then Exponents or Roots, then Multiplication or Division, then Addition or Subtraction in the order you see them). It worked well for that student and was passed around and I many different versions and some not so clean. So consider using memory tools but help the kids develop their own.