When you sing, it is important to control how much of your breath comes out, so that you don’t run out of breath too quickly. This is called breath control. Here are some exercises to help you improve your breath control.
Slowly blow up a balloon, using slow sustained breaths controlled from the diaphragm. The idea is to take a comfortable deep breath and then breathe into the balloon using an even, sustained amount of air pressure. Repeat this until the balloon is full.
Sing the sound "la" and keep it sounding for as long as possible before you run out of breath. The less force you use as you sing, and the more you breathe from your abdomen, the longer you will be able to keep the sound going.