Place your palms on the ground and the crown of your head in front of your hands close to a wall, forming a triangle with these three points of contact.
Flatten your back against the wall, and extend both legs up and against the wall.
Put some pressure on your hands for stability; don't let your head take all the load.
Risks
This exercise puts a lot of pressure on the head. Make sure to warm-up your neck thoroughly before starting.