Belly breathing improves the supply of oxygen to the blood and brain.  It helps relax you, which increases your energy level.  It will also make it easier for you to read and speak.

Standing up, place your hands on your abdomen.  exhale through your mouth in short little puffs.  Next, inhale slowly and deeply, fillling your abdomen like a balloon underneath your hands.  Slowly and fully exhale the air.  repeat this a few times, making sure you have a natural rhythmn going.