Goals of a single class
There are lots of thoughts about the multiple methods of communication and motivation, but equally important is the overall structure of a class. Gone are the days when kids and adults had afternoons free to spend hours upon hours on their hobbies and education. For better or for worse, the modern lifestyle is one of structure and, when working with parents and their kids, a balance of available transportation.
With this in mind, the structure of a class has to contain balances of energy/focus, application/philosophy and challenges/progress.
Energy: A good physical workout is always nice to have in a class, but - more important than that - is the energy of the class that inspires everyone to do their best. A simple, classic workout energy can be boring, unless it has good spirit.
Focus: On the other hand, helping a class learn something - no matter how big the class is - is impossible without a certain amount of focus. No, making everyone stand in resting position while the teacher pontificates for - seemingly - hours on end, is not the solution. That being said, a class with so much energy that it doesn't have any direction doesn't help anyone either.
Application: Everything we practice in martial arts has a practical application to it. Some may be tangible the very first day of practice, like a high block, and many take years of practice, like a circular block. However, both have practical applications to it. Never underestimate the importance of a class practicing a technique and then taking some time - even if it is only seconds - to make sure everyone understands what they are trying to accomplish.
Philosophy: The "Way of Karate" is - ultimately - that of philosophy. Students practice for years and years on end to become mentally stronger and more flexible to handle life's challenges. It is important that instructors work hard, every class, to touch upon this. Reciting the student creed is an easy way of getting this done. So is explaining why and encouraging a student the important to practice a kata that that student may already be proficient at.
Challenges: The very nature of being a martial artist is to challenge him or herself. Instructors should be challenging their students every class. Careful attention must be placed to make sure that the student's spirit is up, but it cannot be denied that the best way to strength is by overcoming challenges.
Progress: At the end of every class a student should walk away sweating, energized and thoughtful of what he or she needs to work on to improve. Nothing encourages a person more than a sign of progress. The belt ranking system goes a long way with this, but nothing beats a good "pat on the back." Some progress is harder to see then others, so it is the Instructor's job to highlight them. Students seeing their own progress goes a long way with encouraging them to take the next step or to work harder on the current one.
Combining all these goals into a single class ensures the success of the students and encourages them to come back for more!