A simple article found on singing tips by Vocal Coach Yvonne DeBandi reproduced below:
A = Airflow.
Never hold your breath while singing. The airflow is what creates and carries your vocal tone, so keep it flowing. Avoid Clavicular Breathing and Belly Breathing — instead, learn the proper way to breathe for singing, called diaphragmatic breathing. Fill the lower portion of your lungs as if you had an inner tube around your waist that you were evenly filling.