First of all, you could go and try different types of yoga to see what suits you. It could be confusing to just go to one class. Next, interview the teachers. Find out where they studied and for how long. Did they just pick up a book or take a six week course, or did they actually go to school or back and forth to India? Find out about their certifications. Do they know enough to keep your body safe? If you have a health condition like heart disease or pregnancy, do they have the experience or the training in that sort of thing? An experienced teacher would be able to give you an alternative posture or practice rather than having you sit out until the class reaches the next posture. Look for someone who will make you feel good when you've left the class, even if you have some sore muscles for the first few weeks. You need to feel like yoga has really enhanced your life, your well-being, and your health.