Once you put yourself in a posture you should try and keep steady for some time instead of doing repetitions. The postures have being carefully developed to give you both a healthy body and mind by emphasizing on balance. A good instructor will take the class through a whole range of movements and counterbalanced postures. For example a stretch to the left will be followed by a stretch to the right and so on. At the end of a class you should feel refreshed and revitalized and not strained or exhausted.
Breathing is the key to Yoga.
Most of us do not use our lungs to their full capacity. Awareness of breathing is very important. By inhaling and exhaling you help your body gain posture and keep balance. So if you are interested in getting fit and in regulating your weight, in becoming more supple and fighting back problems, in learning how to relax and relieving stress then indulge in some gentle exercises that involve a little philosophy. Join a yoga class.