Sheilding usually involves gathering a lot of very compacted (almost solid) energy into a protective 'bubble' around the creator. This is something that could protect you from a variety of things, like to filter energy for a psi to take in or help any vampire to keep energy from escaping.

Basic Shielding Technique:

Simply visualize yourself surrounded by a protective circle of white light. Or you can envision yourself encompassed by a cone of white light. When you are able to hold the vision solidly, your shield is up.

Advanced Shielding Technique:

~This is a bit harder to hold & should be practiced to achieve its full effect.~

Visualize yourself surrounded by 4 mirrors (with the reflective sides facing away from you). They should all be touching, forming a solid box. Once you are able to clearly hold this add 2 more mirrors. One above & one below, also facing away from you. You should now be unable to see yourself at all. Only a complete "box" of mirrors. Once you are able to clearly hold this visualization, your shield will be up.

~ more here ~