Diaphragmatic breathing for vocalists is essential for consistent tone quality, volume, and vocal health. It can sometimes be difficult to activate the diaphragm if you've never done it before. The key is to notice where your body expands when you inhale.
There are dozens of breathing exercises published for vocalists. I use one. Yes, one! I call it The "Hissing Tire" Exercise and I rarely need anything else.
Here's how to do it:
Using singing posture, slowly inhale through the mouth, silently.
Be sure to feel the air expanding low around your waist. (If your shoulders rise, you're not breathing diaphragmatically and you will not get the results that you desire.)
As you exhale, make an "Ss" sound as if you are a leaking tire. Be sure to flex your abdominal muscles as you exhale. (This is how you support your singing. It will give you control, volume, and endurance! Really good stuff!)
Set a goal and time yourself to see how long your exhale lasts. (I usually start with 15 or 20 seconds.)
Every day, increase your goal by 2-5 seconds.
Over time, you should be able to reach 30-35 seconds or even more. You may reach a plateau and that is okay. You may find that some days you regress. This can be due to fatigue or dehydration. Don't worry, if you keep practicing the "hissing tire" exercise, you'll get right back on track.
WARNING: This exercise can cause hyperventilation and you should only do it two or three times in a row. NEVER more than three times! You will become dizzy and could faint!
As you work on your singing repertoire, make diaphragmatic breathing a habit. You'll find yourself with more control, more stamina, and beautiful sound!