Our ancestors have viewed the dead with a strange mixture of reverence and fear for thousands of years, and leaned more towards one end of the spectrum or the other depending on the culture. For some reason, they "knew", through some channel, that the dead weren't always happy-go-lucky and willing to pass on peacefully. That, of course, follows us into modern times where now we don't necessarily have more death and more violence, but its generally a bit more shocking to us than it was during the Dark Ages. This naturally leads to some rather unhappy geists.
That being the case, those of us who do decide that working with the dead is an appropriate praxis are soon confronted with the task of discerning the nature of a spirit and learning to protect ourselves from it if something goes awry and the feces hits the proverbial fan. As indicated in previous posts, I've been doing this sort of work for many years, I've had my fair share of really nasty things show up, and I've got many scars from it: nightmares, scars from being cut, a scar from a gunshot wound, etc. so its not something for the faint of heart.
In the Norse cosmology, one protected himself by scrawling containing runes on the barrow in which one (who was thought to be aggressive or restless) on the tomb. When the dead showed up, the thought was that light would take their power away, but other than that, silver was of import, as were runic charms. In my practice, I've found that using the appropriate galdrar, or projecting the appropriate rune(s) at a target would bar him or her from manifesting, thereby negating the threat. Other practices involved lopping the dead guy's head off and putting it between his feet, burying the individual face down, or simply burning the corpse. Those methods, while effective if we're dealing with zombies, aren't going to cut it when dealing with a disembodied corpse.
So, I'm sure, at this point, that you're asking yourself "well, if those methods aren't going to work, what can I do?" It is at this juncture wherein we meet the meat of this post. If the spirit in question seems aggressive, your first line of defense can be prayers, projected sigils of intent, blasts of energy, or countless other methods. Here are a few of my favorites, escalating in force:
1) Trace the rune Stan, pictured below, and project it at the spirit in question. The rune Stan is a boundary stone, and can be used to block a spirit's manifestation.
If you find the need to appeal to Her, you may do so using this prayer:
"Om Tare Tuttare Ture Soha (repeat thrice)
Homage to you, Smashan Tara-Ma
Whom presides over those who are dead and gone
Whose TURE destroys the Great Fears,
Those deathly shades and demons,
With a wrathful frown upon Your face
Homage to You whose powers of invocation
Call upon the local protectors,
Removing all threats with the letter OM
You bring peace where there once was none
Lay these shades to rest
Remove their burdens
Give them peace
Om Tara Tara Trey Pey Om (repeat nine times)"