Pranayama is very subtle. For this reason, in Iyengar Yoga we go extremely slowly with it. With asana it is different – an experienced teacher can see what is going on and correct straight away.
When you make your exhalations long, feel the abdomen go down. Do not allow the abdomen to go forward at the end of the exhalation. On the contrary, allow it to go straight up. You don’t have to pull it in. It pulls itself in. The moment you stop exhaling is as if you allow your consciousness to sink down toward the base of the spine.
Your first inhalation will be somewhere below the navel. This is a very important part of the practice, because with it come two bandhas: mula bandha, and uddiyana bandha.