How to do it:
Step 1: Sit down on the ground in any meditative pose keeping your eyes closed and spine neutral.
Step 2: Take long breaths in and out through your mouth, feeling the air passing through your windpipe.
Step 3: Once you are comfortable with your exhales, contract the back of your throat to constrict the passage of air. Your throat will start making a rushing noise while breathing.
Step 4: Once you are comfortable with exhaling, constrict the throat the same way while inhaling.
Step 5: When you can contract your throat while both inhaling and exhaling, close the mouth and start breathing through the nose.
Step 6: Fill your lungs, hold your breath for a while and then exhale.