Breathing correctly is one thing I have been currently stressing with my patients. 22,000 reps per day better be good. That is how many breaths they say an average person takes. Then, tie the breathing in with proper scapula motion on top of the ribs. I often find the scapula to be "stuck" to the ribs. Usually only one. I wedge my fingers underneath the medial border. Sometimes this is very difficult for me and for the patient. Sometimes I physically can't do it. If this is the case, this shoulder blade hasn't moved correctly in awhile. I then show them the other side, usually much easier.
Once I do manage to get the fingers underneath the scapula, I ask them to take a deep breath in through the nose and talk about expanding the ribcage. I will hold my opposite hand on their same side traps and tell them I don't want this hand to be elevated when they breath in. This gets rid of the shrug breath. In through the nose, out threw the mouth. When they get the idea of rib expansion, the scapula starts to move and the ribs expand and push my fingers out from underneath the scapula.
So my cue is, "Push my fingers out from underneath your shoulder blade with just your breath. Big breath in, expand those ribs. Keep my top hand on your traps quite. Usually after a few tries, they get the idea and start to get those ribs moving through the diaphragm.
This is something I will do with all shoulder/neck/thoracic spine dysfunction. Breathing gets a lot of things moving better. I found this to be a helpful little physical cue into getting them breathing better. Give it a shot.
If you were interested in a great article on the anatomy of the diaphragm and why it becomes so important, I highly recommend this paper. Best anatomy of the diaphragm paper I've read. Anatomy of the diaphragm.