(nah-dee show-DAH-nah)
nadi = channel
shodhana = cleaning, purifying

Step by Step

Sit in a comfortable asana and make Mrigi Mudra. Beginning pranayama students may have some difficulty holding their raised arm in position for the length of the practice. You can put a bolster across your legs and use it to support your elbow.

Gently close your right nostril with your thumb. Inhale through your left nostril, then close it with your ring-little fingers. Open and exhale slowly through the right nostril.

Keep the right nostril open, inhale, then close it, and open and exhale slowly through the left. This is one cycle. Repeat 3 to 5 times, then release the hand mudra and go back to normal breathing. (NOTE: some yoga schools begin this sequence by first closing the left nostril and inhaling through the right; this order is prescribed in the Hatha Yoga Pradipika, 2.7-10).

Traditionally Nadi Shodhana includes breath retention, fixed ratio breathing, and the repetition of certain "seed" mantras (cf. Gheranda Samhita 5.38-54). For beginning pranayama students, it's best to focus only on the inhales and exhales.