A great time to use breathing techniques would be before a test or an exam, when anxiety tends to run high. Breathing is also great for transitioning between one activity and another.
Deep Dive Breath
Hold your breath and squat down like you are going underwater - pop back up when you run out of breath.
Rise and Fall
Lay on the floor and place an object on your belly and watch it move up and down while you breathe.
Flower Breathing
Close your eyes and pretend you are smelling a flower. Watch out for bees!