Setup and Key Actions
Stand with your feet a little wider than hip-width apart (about the distance of the short edges of your mat). Bend your knees and place your hands on your thighs. Bring the weight of your torso over your arms (avoid bending your elbows) so that you can start with a relaxed belly. Look down toward your belly. As you exhale, engage your pelvic floor, followed by your lower belly (laterally, between the two frontal hip bones, and horizontally, between the pubic bone and the navel), and the the upper belly (navel to spine). Release the upper belly, lower belly, and pelvic floor as you inhale. Repeat this 5 to 10 times, or add uddiyana bandha, the abdominal lock.
To add uddiyana bandha
Exhale, contract the pelvic floor, lower belly, and upper belly. When the whole abdominal wall is contracted and the breath empty, suck the belly up under the ribs. Then immediately release the suction and inhale, releasing the contraction in the upper belly, lower belly, and pelvic floor. Without pausing, exhale and repeat.
Modifications
Stand with your hips against a wall, or practice on all fours for more stability. If the three-part squeeze is contraindicated for you (common contraindications include hiatal hernia, high blood pressure, heart disease, pregnancy, and menstruation), then stick with a gentle squeezing and releasing of the navel toward the spine.