Most instructors line their students up and count off the techniques while watching. After demonstrating a concept, they let the class try it out, but only the very few go from person to person adjusting each and every student they can during an exercise. Good instructors spend their time in the midst of student correcting them, riding them, fussing over their abilities, and coaching them to higher performance. There are several subjects that a good instructor should be versed in before he runs out onto a pretty wood floor to give others his wisdom, but most never bother. Education - Good teachers are born, not made.
Good teachers are rare.
However, the topic of how to teach others has been studied and documented to a high degree. Anyone teaching others should probably subject themselves to some training on how to do it. Enthusiasm - No matter what kind of person you are, training through grueling, repetitive exercises is easier when you have an instructor who yells, jumps, howls, and threatens you to higher and higher performance. A loud voice and an exuberant personality are good qualities in a leader. Teaching to the class is a terrible way to convey karate.