1) Voice Quality: Depending on the class you're teaching you need to make sure your quality and tone support. Additionally, your voice quality must change throughout the class. In the beginning a calm and steady voice invites the students to be present. If teaching a vinyasa class, your cadence and directness must increase as the flow-tempo increases. At the end, in savasana, once again a calming, soft voice is required.
2) Vocal Energy: Your vocal energy must match the class you're teaching. Broadcasters rely on finding the "mood" of the story to determine their energy. In yoga...it is the type of class. For a slow-flow Hatha class, NO ONE IS WANTING A CHEERLEADER! However, after 45-minutes of a Vinyasa 3-4, a little pep just might be what the doctor ordered. (sorry won't unbold!)
I kind of wish I would have thought about this on Day 1, instead of Day 24!