How do I practice alternate-nostril breathing?

Here's how to do alternate-nostril breathing:

• Sit in a comfortable position and close your eyes.
• Exhale fully.
• Close off the right nostril with your thumb and inhale slowly through your left nostril. (Traditional yoga texts instruct a person to make a gentle fist with the right hand, and then open only the thumb and the last two fingers. The side of the thumb is used to close off the right nostril, and the side of the ring finger is used to close off the left nostril. In practice, though, do whatever is most comfortable for you.)
• Close off the left nostril and exhale through the right nostril.
• Inhale through the right nostril.
• Close off the right nostril and exhale through the left nostril.

Continue this pattern. In other words, change nostrils after each inhalation. If you can do it comfortably, gradually increase the duration of your exhalations until they are about twice as long as your inhalations. Continue doing this for thirty seconds to three minutes. If at any time you feel like you're not getting enough air, simply resume breathing normally.