Place the crown of your head (the small place where a book would balance if you were trying to balance on with excellent posture on your head) onto the mat and place your palms flat shoulder width apart. The elbows will stack directly above the wrists and the elbows hug in to form a 90 degree angle. Curl the toes under, lift the hips and walk the feet in. Take one knee and place it lightly onto the tricep following with the second knee. Don't let the arms buckle under the weight of the legs. Keep pushing the triceps into the knees to create resistance and aid in keeping the shoulders away from the earlobes and the neck long. Keeping the big toes and inner heels touching, begin to pull the belly in and lift the knees up off of the arms. Once the legs begin to lift and straighten, squeeze the inner thighs together, spread the toes and lift towards the ceiling. Shoulders stay lifting, ribs in. Keeping the inner edges of the feet touching, bend and spread the knees lowering them back onto the arms. Snuggle them as far up towards the armpits as possible. Now, think in terms of threes: Roll towards the bridge of your nose trying to look forward, drop the bottom, gently dig the fingertips into the ground to help pull the chest forward. Once you master lifting the head, round the upper back and push the ground away. Take a few breaths in crow. Tuck the chin, place the crown of the head back onto the ground and pull back up into full headstand. From here either lower with bent of straight legs. Rest!
*If the full headstand is too intimidating, try to lift into crow from the prep (knees beginning on the arms).
Here you go. There's also a full-breakdown of both Crow and Tripod in my Aim True DVD: