How we put the left or right foot forward (to begin yinning and yanging, pronounced “yahning”) is demonstrated in these photos.
The back heel lifts off the ground as the weight shifts forward, and then the front toes rise as the weight shifts to the back leg.
These positions apply only to the front-to-back movements. See “Carry the Ball to the Side” for a description of the sideways “T’ai Chi step” and how it applies to movements with a side-to-side foot position.