The key points to observe in T’ai Chi Practice

1. Relax the neck and suspend the head from the crown point.
2. The eyes should focus and concentrate on the direction in which the ch’i flows.
3. Relax the chest and the back.
4. Drop and relax the shoulders; drop and relax the elbows.
5. The wrist should be set comfortably while the fingers stretch outward.
6. The entire body must be vertical and balanced.
7. The coccyx must be pulled forward and upward with the mind.
8. Relax the waist and the juncture of the thighs and pelvis.
9. The knees should stay between relaxed and not-relaxed.
10. The sole of the foot should sink and attach comfortably to the ground.
11. Clearly separate the substantial and the insubstantial.
12. Each part of the body should be connected to every other part.
13. The internal and external should combine together; breathing should be natural.
14. Use the mind, not physical strength.
15. The ch’i attaches to the spinal column and sinks into the tan t’ien
16. Mind and internal power should connect together.
17. Each form should be smooth and connected with no unevenness or interruption, and the entire body should be comfortable.
18. The form should not be too fast, and it should not be too slow.
19. Your posture should always be proportionate.
20. The real application of the form should be hidden, not obvious.
21. Discover calm within action and action within calm.
22. First the body should be light; then it will become limber. When limber it should move freely. Whoever moves freely will be able to change the situation as needed.

Reference:
Waysun Liao Tai Chi Classics
ISBN 1570627495
p. 126-127