Just before going to bed, fill a cauldron (or iron bucket, bowl or pot) with water and place it inside your house near the front door. Take a very sharp knife or Athame and place it point-down into the water, saying:
“Into the water I place this blade,
To guard against the thief and shade.
May no flesh nor astral shell
Enter this place wherein I dwell”
This is a good protection spell, and can be performed every evening. In the morning, remove and dry the knife, and place it somewhere safe. Then, without touching it, pour the water outside, (or down the drain if necessary) and put the cauldron away. It probably wouldn’t be a good idea to do this spell if you’re expecting company, as it could be dangerous (and wet).
You can do this at each door if desired, and protects against more than corporeal forms.