You need a strand of your hair, an nail clipping, a drop of blood and boiling water.
Mix them together whilst saying
"I beg to be wolf in dark and light
I beg to be a prowler of the night
I beg to thee to make it soon
I want to be wolf at the next full moon"
Bury the mixture under a tree, and wait untill the next full moon. When the next full moon comes, go back to where you buried it, water it. And you will feel a strange feeling, then you should change.