We are meant to sing!
I really believe this. From the tops of our heads to the soles of our feet, our bodies were designed to support singing. For those who naturally sing well, all those components naturally work together. But for those who don't, those things can be learned; muscles can be identified and strengthened, posture can be improved. We study a lot of physiology (according to the comprehension of the student) and how to identify the support and sound mechanisms of the body in order to improve our singing.
In addition to this studying (such as breathing and muscle control) we study solfege, vowels, sustain, music theory, and of course, their songs. I think it's important that the singer be able to understand music reading basics so that they can at least read their own music range. If the student is unfamiliar with this, we add it to our lesson plan.
Ideally, we need at least a half hour for singing. If we need to add other music theory, 45 minutes is a better alottment of time. I charge $20 for a half hour session, $25 for 45 minutes.