To create a protective shield around you or your home, choose a color that represents protection to you. It can be white for the Goddess or purity, blue for peace, whatever feels right to you. Imagine this color blanketing you or your home and surrounding you in a bubble. Visualize it repelling negative forces that come towards you, and watch them bounce off and return to their sender, gaining speed as they travel away from you. The more detailed your visualization, the more powerful your shield.
Make sure that you continue to visualize this shield daily to keep it strong.