Please take a look at this video
and observe the abdomen of the gentlemen wearing the blue cloak. What you see is referred to as a SPLAT breath – SPLAT stands for : Singers – Please – Loosen – Abdominal Tension.
Ladies in particular hold their bellies in and that creates tension which doesn’t help proper breathing for singing. Before you even breathe in I suggest you first of all fully let go of any tension in your belly by just letting your belly fully relax. That stretches the abdominal muscles which are thus lengthened and then pull on the diaphragm to which they are attached. At that point the diaphragm will descend and automatically air will flow into the lungs without any effort at all and depending on the length of the phrase to be sung that is all you may have to do.
If you need a top up then aim to fill up from the lowest part of your lungs first, your lungs go right down to the point of your lowest rib and as you need more air for a particularly long phrase you can top up from the bottom of your lungs. Think of blowing up a balloon that is open end up in your lungs.
Once you have the breath you need for the phrase to be sung you need to allow it to flow under control, if it escapes too quickly then you will run out of air and if you conserve too much of it you won’t produce a big and rounded sound.
You control the escaping air by contracting your pelvic floor and abdominal muscles and keeping your rib cage up (avoid leaning back). Keeping the rib cage up is hard as it naturally wants to go back to original position before the in breath.
Exercise
Just take a few breaths as if for singing and be aware of what you are actually doing, where does the breath go? Are you relaxing your belly?