Setup and Key Actions
Stand with your feet together, but heels slightly separated or with feet hip-width apart (about four to six inches or “two-fists’ distance”) and parallel. Center your weight over the arches of your feet. Ground down through the mounds below your big toes and your outer heels.
Line up the back of your skull with the back of your tailbone. Draw your lower ribs back if they tend to jut forward.
Rest your arms alongside you with palms facing in or forward. Broaden through your chest and collarbones.
Root down through your feet and lengthen up through your crown. Relax your face and jaw.
To find your ideal alignment, try practicing at a wall. Stand an inch or two in front of the wall with your feet hip-width apart and parallel. Keep your bottom, the backs of your shoulder blades, and the center of the back of your head against the wall and draw your low ribs back toward the wall if they poke forward. Here too, ground down through your feet and lengthen up through the crown of your head. Relax your face and jaw.
To work more on activating your abductors (outer hips) in mountain pose, make a loop with a yoga strap that's big enough to wrap around your shins yet tight enough that you can push out against it and feel some resistance (you may need to experiment a bit until you find the perfect-sized loop for you). Be sure to wrap the strap below—not on or above—your knees. Parallel your feet, micro-bend your knees (just a tiny bit to avoid hyperextending), and press your feet apart from each other. Try to bust your strap open. You most likely won't break the strap, but you'll probably feel the engagement in your abductors. Keep your low belly active, and if you notice your low ribs jutting forward, gently draw them back.
To work more on activating your adductors (inner thighs), try squeezing a block between your inner thighs (but avoid tucking your tailbone under—squeeze the front of the block a little bit more than the back of the block).