Contract your abdominal muscles to increase pressure in the abdomen and thorax. Your diaphragm will relax and rise upwards, allowing you to better control the sound.
Release all tension from the upper torso, especially in the area around the shoulders. Maintain this state even during the most demanding vocal sections.
Keep the rise and fall of the diaphragm slow. Instead of moving the diaphragm itself, focus on the back and abdominal muscles that influence it.
Ensure that your ribs remain in an outward position, to the furthest extent possible. Retain this posture without pushing the muscles out or downward.
Maintain an elevation in the rib cage and sternum. Practise achieving this by lifting your arms above your head and suspending the breath. Lower your arms while you exhale, without allowing the sternum to lower.
Recognize the feeling of buoyancy achieved by the correct breath management. Develop this feeling while singing and hold it for as long as comfortable.