As an exercise teacher and someone who has enjoyed yoga classes for years the only other thing I would add is not to be intimidated if the teacher corrects your posture during the class. They will be wanting to check you are stretching correctly so that they can ensure you won’t do anything that could injure yourself. A good teacher will also have asked you lots of questions about your health and exercise history so that they can check whether there are any exercises that will be particularly good for you or any that you should avoid.