This is an 11 page primer I wrote for Astral and Psychic Defense. 
I am making it available for nearly free in hopes that it will reach more people. 
 
This primer will walk you through making a psi ball, changing the properties of it, and converting that psi ball into a basic shield or item. It provides numerous ideas for exercises that you can do to refine your energy manipulation skills, while learning to defend yourself astrally.