So we have been looking at ways to do The Complete Breath. here & here And breathing to stimulate the inner fire here, plus breathing to cleanse the frontal lobes here.
I find it easier to get students to do complete breathing at the front of a class, or in the pranayama section at the end. And, it is easier to teach it as a stand-alone pranayama at the end of the class, prior to relaxation or meditation.
But sometimes I start with an easier breath, which people often call the abdominal breath. This quickly calms & brings the mind to one-pointedness. Then I encourage it through out the class. It's done similarly to the complete breath, but is also not at all like the complete breath! I started teaching in this way as I could see that people were not relaxed in a class. And were therefore straining & overheating. (Two of my bug-bears). Abdominal breathing calms our emotions, & in this way, calms the ever-fluctuating mind. So, it's an absolute blessing. When the mind is calmed, the Higher Realms can be effortlessly reached.
Put one hand on your navel. On your next exhale, gently draw the navel back towards the spine. You could say "draw the abdomen back to the spine", if you prefer. Release the abdomen to breathe in. Continue for a few breaths. Move into doing a tiny pause after each inhale & after each exhale. The wee pauses are like the icing on a cake.....they add the finishing touch to the abdominal breath, & take it to the next level. Surprisingly, this type of breathing gives longer endurance in a class.
Doing the abdominal breath in this way, leads one easily into ujjayi. Ujjayi is sometimes called the Victory breath, the Psychic breath, the Whispering breath. I was taught decades ago, to use it for teaching for heart recovery, such a s strokes. Unfortunately, over the decades I have noticed that it was being taught quite strenuously. I was originally taught to constrict the glottis as I breathed in & out, to make a soft noise, & doing it this way did seem to encourage some people to be very loud with it. It isn't supposed to be about loudness. And with the glottis constriction, some people would tense their jaw. This is counterproductive to stress release.
Swami Janakananda stayed with me once, & proclaimed that ujjayi was being incorrectly taught in Australia & New Zealand. These days I teach it in a more sublime way:
Using the abdominal breath, with the tiny pauses, open your mouth as you exhale, quietly saying "ha-a-a-a". Inhale through the mouth. Do this a few times. Then add: "a-a-a-h" with the mouth open' for the inhale. The sound being made is very soft, & the breath sort of skims backwards/inhaling, & forwards/exhaling, along the upper palette. Try it, ujjayi this way is beautiful: instant happiness! There is a gentle stimulation also to Lalana chakra, in the upper throat.
The abdominal breath is a stand alone breath which can take you very easily into meditation....just keep doing it, & add so/inhale; ham/exhale. Ham sounds like "hum". Do it for a few minutes.
You can also add ujjayi to this, making it even more relaxing & profound.