Ok, so this is the most difficult in the series of right postures. Even I am not sure of how to explain and even I have not yet practiced it accurately that I can tell you how to do it. It is said that you should pull your shoulders back but it is no where specified how and how exactly to do without looking too stiff. One thing I can mention is that pull back your shoulders only a little so that they are parallel to the hips when you are sitting or standing. Generally, they are not coz we tend to slump forward a little. This would cause your chest to come a little forward and make your breasts look firmer.
But, do not make the position so stiff that the muscles of your back start to ache. So, try various positions and select the one which is most comfortable and makes you look a little upright than what you currently are. That would mean you are pulling your shoulders back. Ok, one more thing which I would add before concluding this series is that pull your whole body into an attention position when you are standing but without looking too stiff so that it looks as if you have all your body parts in control without being too uncomfortable. Generally, it is also said to suck your stomach inside but I wouldn’t recommend that as it makes it difficult to breathe deeply. Another sign that you are holding the right body posture is that it allows you to breathe deeply without too much of an effort.