Use due diligence. Check out a few instructors and cross compare. There needs to be more happening in a class than just the physical part. They don?t need certification, but should at least know both the common and sand script names of each posture.
People come to yoga to find themselves. Stretching releases tension, but there?s also a meditative, spiritual aspect. ..You are going to get physical benefits, and that?s fine. But if you have the right teacher, you?re going to get all the other stuff, too.