For those who are not familiar with this pose, it is just physically standing up with your feet together and arms down at your side. As you observe someone in an aligned Mountain Pose from their profile, the ear canal will line up with the center of the shoulder, the middle of the chest is right over the middle of the pelvis, and the middle of the pelvis is right over the front of the heels.
To break your habitual way of standing, try this playful exercise:
Stand up with your feet together. Bend your legs and feel your heels make firm contact with the ground. Maintaining that contact, straighten your legs. When your legs are straight, continue contracting your quadriceps so that your kneecaps are pulled upward. Close your eyes and play with your balance. Observe where in your feet your weight transfers to as you play with your balance.
After making big shifts with your weight, begin to make the shifts smaller and smaller, hovering closer and closer to having the weight fall evenly through both feet and predominantly down through the front of both heels. Play with the placement of your head, your arms, your chest, your pelvis, and your legs.
Capturing the center is not important and not really even possible. But building awareness of your fluid posture and awareness of where your body is in relationship to the earth is infinitely valuable.