What is proper yoga breathing?
—Marion from New England
Read Natasha Rizopoulos's reply:
The kind of breathing generally practiced in most hatha yoga classes is called Ujjayi breathing, which loosely translates as "victory" breathing. This is not to say that the quality of the breath should be aggressive, but rather that there is a steadiness, resonance, and depth to it.
To find your way into this form of breathing, begin by closing your eyes and observing your breath in its natural state. Tune into the rhythm, pace, and sound. Compare the length of your inhales to the length of your exhales. Notice the location of the breath. Focusing on the breath this way is one of the most basic and important tools of yoga, for it is by observing the breath that we come into the present moment, and it is this pattern of observation, linking mind and body, that we want to re-create throughout our practice.
Once you have taken note of the details of your natural breath, start to make subtle adjustments. Begin by matching the length of your inhales to the length of your exhales. Once the breath is even, elongate and deepen the breath just slightly, not to the point where it feels forced or strained, but just enough so that there is a consciousness about it. Continue to breathe in and out through the nose, and then shift your intention. Imagine that instead of breathing through your nostrils, you are instead breathing through the soft spot right between your collarbones, at the base of your throat. Notice how this shift in intention changes the sound and quality of your breath. It is less nasal, throatier, and has a more hollow sound to it. Ujjayi breathing is sometimes compared to the sound of the sea in a shell, or to the purring of a contented cat. The breath should be audible to you, but not to anyone standing more than a couple of feet from you. Sometimes people create a breath that sounds like Darth Vader, thinking that louder is better, but in fact the breath should have a soothing, quieting quality to it.
Practicing Ujjayi breathing is a way of harnessing the mind, using the breath as a vehicle for taking our attention off of our normal thought patterns and re-focusing it on the physical details of the practice. The breath has a function on the physical level as well, for as we begin to move more and the practice becomes more rigorous, it becomes more challenging to maintain a steady, even Ujjayi breath. The tendency is to start breathing through the mouth and for the breath to become shallower and more ragged. Maintaining a steady Ujjayi breath is hard work and thus has a very positive effect upon the lungs and heart. The breath will naturally become deeper and faster with increased effort, but when it becomes impossible to keep breathing through the nose and when the quality of the breath becomes compromised, it is usually a sign to back off and rest until you can resume with an even Ujjayi breath.
Pranayama is a quite advanced form of breath control that is usually practiced separately from asana practice, under the close guidance and supervision of a teacher. In Patanjalis eight limbs of yoga, asana is the fourth limb and pranayama the fifth. Many people take this ordering as an indication that one should have a fair amount of asana experience before taking on pranayama, so I would recommend that you focus your attention on Ujjayi breathing, as this element of the breath is most appropriate and relevant for beginning practitioners.