I'm a very new diver, but I'm getting ready for my 12'th year as a ski instructor, and while the skills are different, teaching them is the same. My thoughts are as follows:
First, a good instructor has to realize that, while safety is first and foremost, the student is there for a recreational activity.
Every student learns differently, we are taught in PSIA (professional Ski Instructors of America) that the 4 basic types of learner are "Seer", "Doer", "Thinker", and "Feeler" there are technical terms, but i don't go too much for jargon
Anyway, the instructor must be prepared to deal with all types (most people are a combination of the above) simultaneously in the group. This is hard at first, but eventually the instructor builds the "bag of tricks" to help most of the common situations.
The customer must be dealt with with respect, what is obvious to an instructor with years of experience is new to a rookie. Example, I never laugh at a student who puts their ski boots on the wrong feet, it happens.
A good instructor must be able to deal with a student who is nervous, or a student who is overly cocky, without making them feel bad about themselves, or let them get into trouble.
A good instructor must be aware that every human body is different, and deal with that on an individual basis, for example, when a student has trouble with cold, or heat, or equalizing (like I did) to give specific technique tips, not "just equalize and go down" like MY instructor did.
A good instructor knows that there are no stupid questions, and answers each one
patiently and without condescension.
The good instructor treats staff with respect, especially in front of students.
He cal allay the students concerns with knowledge, and takes the time to do so without taking them lightly.
There is more, but thats my general idea.
andy