A beginner who is just learning the form needs to think about what he/she has learned, and is trying to do. But once the student doesn’t have to think about the movements anymore, this question tends to come up. Why? Because now that the general movements are part of “body memory,” the mind tends to begin to wander. In pops thoughts on, “What should I make for dinner?”, or “I wonder why my boss was so upset at work today…” There may even be an “am I doing this part of the form correctly?” question coming up there, but this type of question is only marginally better than the other distracting thoughts.
Ideally, when practicing the form, you should keep your mind empty. No pictures, no words. (You might want to read our article on Tai Chi as Meditation which further discusses this.) However, while not thinking any thoughts, pictures or words, you should be feeling the straightness of your spine, the bubbling well spring in your foot, your weight distribution as you go from posture to posture, and the texture of the air. You cannot focus on all these things at one time at first, so add them one at a time. When you can comfortably do one thing, add another. Eventually you will be able to think of nothing and concentrate on all of the feelings in your body as you practice Tai Chi.
And when you are able to concentrate on all of the feelings in your body while practicing Tai Chi, so many other doors will open to you. Better ch’i flow, improved Push Hands sensitivity, deeper meditation… but I am getting ahead of myself! Let’s save some answers for another time.