When I first started learning the breath I would imagine filling and deflating like an inflatable raft, or the ballon at the water gun balloon game at the carnival. The top of my head and fingertips would be the outer edge of the inflated balloon. This visualization really helped me to understand the relaxation and the path of chi. Breathe in as the balloon inflates and exhale as the balloon deflates. At the beginning of my training, I did not realize that the breath should ever stop at my head. As I practiced more I would imagine the breath passing through my head, feet, fingertips and body into infinity. At first, it was difficult to visualize. One day in a meditation class I listened to how the bell rang and I followed the sound until it disappeared. I began to practice with my breathing the same way.
This morning I was practicing and was paying attention to remaining in my hips, legs, and waist. As I breathed in I imagined the top of the Tai Chi ball was at my sternum and the bottom was at my feet. When my breath filled the ball it would pass gently through its imagined edge and extend up to my back, out the top of my head, through my arms, fingers, legs, feet, etc. This really helped me to keep my attention in my center.