Bikram Yoga SLC instructor Naomi Franchetti at the 2011 National Championships.
Always start with the right grip in the pose. The thumbs should be included with the rest of the fingers, thumbs on the outside, fingers on the inside.
As you exhale, lower your chin to your chest, round your shoulders away from your ears, and tighten your abs. Imagine rounding your spine as much as Naomi is in the above photo.
Curl forward until your forehead touches your knees and the top of your head touches the floor. Very little weight or pressure should be on the head. Only about 15% of the body weight should be in the head. The rest of the weight is in your arms pulling on your heels.
The dialogue will always encourage to lift the hips up, which is important to the pose. But it is important to never sacrifice the grip to get the hips higher. Remember,it is the grip and pull that create the force to stretch the spine.
The harder you pull on the feet the better of a compression you will create benefiting the organs.