Nodi Shodanam, or alternate nostril breathing, has several variations. The purpose of each of them is identical - to cleanse the subtle channels of energy within our mind-body. The result of even a brief practice is a sense of inner calm and balance; perfect for a quick reset, as a tool for self-regulation in a stressful situation, or as preparation for relaxation or meditation.
To begin, sit in a comfortable position with your spine straight and your body relaxed. Take the time you need to feel grounded and stable.
Use the fingers of your right hand to gently close one nostril as you exhale out through the other. Then close that nostril (using very light pressure) and inhale through the first side. That's 1cycle. Close that nostril again and exhale through the opposite side. Lightly close the opposite side and inhale through the first nostril. That's the 2nd cycle. Do one more cycle and then rest your right hand on your lap and breathe normally 3 times. Then repeat that breathing pattern, starting on the opposite nostril.
Here's what the right hand position looks like - Vishnu mudra or Yankee mudra:
After you've completed 3 cycles on both sides with a 3-breath pause in-between, sit for a little while and experience your breath in the nose. You may also be drawn to observe sensations of coolness and openness in your forehead.
And then, move on to whatever comes next, be it meditation, asana, relaxation, or the rest of the day.
Here's the video version: