Part 2
Situational Awareness, Observation and Communication
A good instructor is aware of the class tempo, students' learning ability, safe weapon handling both on and off the field, etc. A good instructor is not someone who talks at students. Rather he is someone who engages the students in meaningful discussion.
Good communication skills include active listening. The good instructor listens to his students, reflects on their comments and addresses their points. While communicating with the students the good instructor is aware of things like body language. Body language can tell an instructor when a student is bored, unsure of himself, confused, etc.
What is the instructor's job while a class is running a drill? What does a good instructor do during a break? The good instructor is constantly watching and analyzing his students. He is looking for small changes a student might make to perform better. He is looking to see how a student is conducting himself even during a break; this might tell him if the student is handling himself in a safe manner in the "safe" areas or if the students are all staying hydrated. He is making sure the students aren't in need of some help maintaining weapons or gear. He is constantly alert and observing.
Don't "dumb down" the class
A potential problem in any class is the instructor having to "dumb down" the class to the lowest common denominator. This means the class is taught at a skill level suitable for only the slowest or less skilled of the students. In my experience this is more of a problem in more advanced classes but can also happen in even the most basic classes.
This might be done for safety reasons. Regardless, it can lead to the more advanced or skilled students becoming bored with the class. This can throw off the entire class tempo. It sucks but it does happen.
A really good instructor though will find ways to work through these problems. Some drills might be altered so students can run them at the pace to which they are most comfortable. It is maybe the hardest job an instructor faces but finding ways to not dumb down the class really sets apart the great instructors from the majority of mediocre instructors.
Safety
Although safety is last on the list it is by no means the least important. There is a big difference between dangerous and unsafe. A quality instructor might run the class through drills that are a little dangerous. Let's face it, guns are dangerous. Every time you step foot on a range there is a certain amount of danger. The key is to not let the class fall into the unsafe side of danger.
The quality instructor achieves a high level of safety through combining all the quality skills already described here - effectively reading the class, effective communication with the class, observing the students and knowing their abilities, etc. Knowing how and when to push the students and when to back off are key traits of a good instructor.
Summary
That's it. Those are my rambling thoughts on characteristics I think make a good instructor. I hope these thoughts help you find your next instructor.