I touched on this subject not too long ago, but bears repeating again: a great master will save you time and tears in the long run. We had a discussion on LinkedIn back in 2013 April about what makes an amazing instructor. Here was my response, which applies not only to martial arts, but to life in general:
I’d have to say things like:
1) Being a living example of what he teaches (not only should he or she have the skills their art is purported to bring, but they should also inspire their students to do their best and to let the dedicated student truly believe, “Wow, it might take hard work, but now I know it is possible to do XYZ”).
2) Ideally, be knowledgeable about his art and its relation to other, related arts (this, I feel, separates a “good” or “great” teacher from an “amazing” teacher).
3) Has a systematic training method that produces results in his students (it’s no good if the master has excellent skills but is incapable of passing them on in an effective manner; this is, sadly, the norm for most of the kung fu and taijiquan masters I’ve learnt from, most of whom said, “You will need 10 years to learn to use this kung fu/ for fighting”).
4) Perhaps most importantly, they should practice high moral values (like it or not, a master’s philosophy will “rub off” onto their students; a jerk will tend to create more jerks).