A good vocal coach should make you feel completely comfortable and at ease in his presence. Just like working with a therapist or life coach, you want to work with someone you trust, who listens to you, and who you're compatible with. You also need tremendous desire and learning ability. The best voice teachers study, read, attend conferences and constantly discuss the voice with their peers.
The passion for learning will take you very far. A good singing teacher does not have to be a great companion, but rather has the ability to play, at least, the most useful scales in all tones. Your ability should be good enough to be able to focus on the student and not have to look at their hands. Being a good, qualified teacher requires more than just the assumption that all voices are the same as yours and will therefore respond to the same approach and methods as yours.
While voice teachers and vocal coaches work to improve singers' skills, they focus on different aspects. Also consider that a teacher can boast of having a long list of “successful” students, including vocalists from famous bands, and may charge exorbitant fees for classes, but these expensive credits and lessons don't necessarily prove that these voice coaches are teaching good technique. It is estimated that half of the working singing teachers do not have a university degree and that only a third have an advanced degree in music. A nicer tone, a wider range, more support and more control over your voice are improvements in your singing that will be achieved with private voice lessons.
If you're a career singer in the middle of singing on stage, you have a lot at stake in your search for a new voice teacher. Having never had another trained, expert, and trained teacher who listened to them and made sure they sang correctly, they may have developed inaccurate assessments of their own vocal abilities and may have received misinformation about the voice they sing. A lot of voice teachers have taught me one or two things that I still use today and I forgot or left behind all the rest. Beware of vocal coaches, especially in the pop world, who claim to be vocal technicians who could function as your only voice teacher.
Understanding a good singing technique is the basis from which you can build the voice you want, be it the strength, range, grain, pitch or any other color of the voice. Looking for what is missing and what is needed in a voice is an important skill for a singing teacher. During my classes, I asked what my teacher was listening to in my voice and why a certain exercise had been chosen. Becoming a freelance voice teacher is incredibly rewarding, but it also means starting a small business.
Working with different teachers and various styles of vocal training will keep you fresh and your voice ready for the challenges of teaching singing.