From Yoga Journal:
Step by Step
Lie supine on the floor, legs strongly extended. If your head doesn't rest comfortably on the floor, support it on a folded blanket. Exhale, bend the left knee, and draw the thigh into your torso. Hug the thigh to your belly. Press the front of the right thigh heavily to the floor, and push actively through the right heel.
Loop a strap around the arch of the left foot and hold the strap in both hands. Inhale and straighten the knee, pressing the left heel up toward the ceiling. Walk your hands up the strap until the elbows are fully extended. Broaden the shoulder blades across your back. Keeping the hands as high on the strap as possible, press the shoulder blades lightly into the floor. Widen the collarbones away from the sternum.
Extend up first through the back of the left heel, and once the back of the leg between the heel and sitting bone is fully lengthened, lift through the ball of the big toe. Begin with the raised leg perpendicular to the floor. Release the head of the thigh bone more deeply into the pelvis and, as you do, draw the foot a little closer to your head, increasing the stretch on the back of the leg.
You can stay here in this stretch, or turn the leg outward from the hip joint, so the knee and toes look to the left. Pinning the top of the right thigh to the floor, exhale and swing the left leg out to the left and hold it a few inches off the floor. Continue rotating the leg. As you feel the outer thigh move away from the left side of the torso, try to bring the left foot in line with the left shoulder joint. Inhale to bring the leg back to vertical. Lighten your grip on the strap as you do, so that you challenge the muscles of the inner thigh and hip to do the work.
Hold the vertical position of the leg anywhere from 1 to 3 minutes, and the side position for an equal length of time. Once you have returned to vertical release the strap, hold the leg in place for 30 seconds or so, then slowly release as you exhale. Repeat on the right for the same length of time.
Benefits of Handstand Pose
You can make this pose slightly easier by raising the lower-leg heel off the floor a few inches on a block or thick book.
If you are especially stiff, do this pose with the bottom-leg heel pressed against a wall. It's also useful to position a block just outside the raised-leg hip. Then when you swing the leg to the side, rest it on the block. The support under the thigh will help you soften the inner groin.
The alignment of your legs, hips, back, and pelvis in this asana will not only aid you in the practice of all categories of yoga poses, but will also teach you how to practice with patience and humility. When you use your intelligence as a guide in your asanas rather than being driven by the goals of the ego, your yoga practice will lead toward a peaceful sense of physical and mental harmony.