Whilst in the Wu Ji standing posture
Ask yourself the following by listening to what is happening in your body when moving. Am I ......
1. Stablising the feet - This means are you feet flat and have softened into the floor. You must not have the uneven weight pressure in your feet (under each foot into the ground) by having more pressure on your instep or outer step. Leaning forward towards the toes or back to the heel can also have an uneven weighted pressure too. Make sure you feel what pressure / weight around the heel is the same under the ball of the feet. Move by using the ankle joint to feel this equal weight under the feet into the ground.
2. Stablising the ankles - This means you are not rocking or leaning while turning the waist and kwa. You do not move the ankle joint at all. If you do you'll the ankle joint will act like a hinge joint and make you lean forward or back while moving placing undue tension and stress on the joint.
3. Stablising the knee - This means you are using the knee joint like it's suppose to naturally work. When rising and sinking or in particular moving the waist / kwa you must make sure the knee's do not move in wards or outwards but follow the line of the foot and if it was following an ice skate blade under your feet not going beyond your toes or hyper extending when rising.
4. Stablising the hips & kwa - This means that the hips are level and you are opening and closing from the kwa (hip joint).
5. Stablising shoulders and hips - This means always maintain a perpendicular line form the hip joint to the shoulder joint when ever moving
6. Stablising the spine / head top - Always maintain the perpendicular line "central axis line" form the nei wan to hu yin (crown of the head to the perineum)