Shershasana [Sheersha means top or head sana means topsy turvy pose. It has to be learned in a gradual, systematic and a careful manner and practiced in a judicious manner to get its optimum health benefits.
Get up in morning. Make sure that the bowels are evacuated completely and satisfactorily. Do not eat anything till at least half an hour after finishing the sheershasana.
If possible take bath.
Take a towel or a napkin and fold in such way that you can keep take it as a soft and firm support under your head.
Sit in a squatting position.
Keep the folded towel in front.
Bend and keep your head on the towel.
Rest the hands by the side of your head.
Stretch your legs in the knees.
Gradually bring the feet closer to you head.
You will experience increase in the weight on your head.
This is called bhooshirasana.
Do this much only for about a week.
After a week when you will be able to lift the legs, comfortably , do so.
The legs may lifted half way.
After two weeks or so you can easily lift the legs completely and make them straight.