The MAN IN THE TRENCH COAT, is a story that I tell at the beginning of the school year, and give examples at the beginning of every unit/topic. I kept a "common mistakes" file for each level of mathematics. The teacher can wait until the student makes such a mistake or "front load" the student, as they explain concepts of a given topic. Not only is it good practice to prepare students of such common mistakes, but also by giving these mistakes a title such as "Man in the trench coat", students