When the Time is Right
Read Ana Forrest's response:
I am not sure what you are referring to when you say "waiting." Waiting for what? I'll assume you feel you have to wait until you've completed your teacher training before you lead a class. If you are currently in a teacher training program, a significant part of that program should be teaching you how to teach. Experience can come from many different places—not only a formal class. If you take regular classes at a studio, it can be educational to observe and take notes while another teacher is handling a class. Assisting another teacher during a class is also a good opportunity to have hands-on experience in a class without holding the energy and responsibility for the entire class as the teacher. It's also a good idea to take classes with other teachers and in other styles of yoga to learn about the differences in language, technique, and instruction.
While it is important to understand many things in and about yoga—such as anatomy, class sequencing, working with injuries, the asanas, and, importantly, the breath—a consistent personal practice, taking private lessons or classes from qualified teachers, and your own study will provide you with a good foundation. If yoga is in your blood and you are passionate about teaching, continue with your program, become certified, and teach!