Choosing an instructor.
A good instructor can make or break a student's perception of a style, or even martial arts
However a good instructor is in the eye of the beholder. And it therefore makes sense that you find an instructor you like, understand, and get on with. Especially since a black belt is a 5 year commitment, your Dan's are an even longer and far bigger commitment.
There are many methods of teaching and many balances between methods that can be achieved. Some students prefer a more physically demanding lesson that will force the best to be drawn out of them through fast repetition and a highly demanding physical program.
Others prefer to understand concepts and learn first through understanding and then through practice and perfection later (mainly on their own).
Like all aspects of life, a balance must be achieved in order to maximize both the physical advancement and technical proficiency. This is always, the most difficult thing to do as an instructor. Unfortunately as classes grow in size, this becomes more and more difficult, and the majority of the class will dictate the method of teaching.
The best method of discovering if an instructor is right for you is to go to classes and give them a try. All instructors will put their best foot forward when a new student is there and a trial lesson will give you an inside look at how the classes are run. This will allow you to make an informed decision about whether or not you like the instructor. If you do not enjoy the first lesson then it is highly probable that you will not enjoy the majority of the classes.
(Remember feeling tired or sore in your muscles is not an unenjoyable lesson.)
It is vital to speak to other students and specifically ask about teaching style, methods, and most importantly, teaching quality. Also remember that you will be working with the other students in the class and it is important to enjoy the students vibe as well. Working with people is the best way to improve.
Most instructors would be only too happy to refer you to a different instructor or style if the first instructor is not for you. Don't give up as there are more styles out there than you can imagine, and many instructors for each style.