Alternate nostril breathing requires closing one nostril at a time. This is done using the right-hand with prana mudra. To do prana mudra, hold the right palm towards you and fold the index and middle fingers towards the base of the thumb. Then gently bring the tip of the thumb and tip of the third finger towards each other. The small finger and third finger should remain together. Keep the elbow of the right arm close to the side of the chest. The right arm can be supported by placing the left palm underneath the right elbow. Bring the right hand up towards the nose. Rest the index and middle fingers on the top lip and keep the tip of the thumb and third fingers close to each side of the nose ready to close the right or left nostril.
When closing a nostril, the tip of the thumb or third finger should gently press against the soft part of the nose just below where the bone ends. This part of the nostril has the smallest space and so only a small amount of effort is required to close the nostril. Also, by keeping the thumb and third finger close to the nose, minimal movement is needed when closing and opening the nostrils.
An alternative prana mudra technique is to extend the index and middle fingers and rest them in between the eyebrows. Everything else is the same.