The first category is made up of chthonic (or geomagnetic) entities, variably called fairies, djinn, black dogs(mothman), etc. Some but not all manifestations called cold spots or hot spots fall into this category as well. Because these phenomena are tied in to geomagnetic activity, they are all quite established, and any effort to get rid of them will only cause more problems than it will solve. What we see when something manifests is a result of the interface of this energy with our brains. In a sense, they are not really there. The brain has to translate such signals into data that can be read by our sense perceptions. To do this, the mind must turn to its "library" of folklore, expectations, and experiential templates to create a form that is not too incompatible with local cultural beliefs in certain preternatural entities. To illustrate my point, imagine the likelihood that an Irish farmer is going to encounter Aisha Qandisha, a Morrocan chthonic entity. It's very unlikely, but many countries do have equivalent characters in their folklore, and these folklores will determine the nature of their experience of those entities. Even cultural trends, such as secularization and the advent of new technologies, will affect how we see these things. Many UFO and ET sightings fit into this category. For another mechan-ism that affects our perception, look below to the Deity category. As for the likelihood of exterminating these "ghosts", well, perish any thoughts you have of ridding your property of these things. Be assured that most (but not all) of them are quite harmless, other than being frightening, they manifest rarely, and they are easy enough to avoid when they do show up. If you simply cannot tolerate these presences it is you who must move away from them, as they were there long before you were.
The next category deals with Qliphothic entities. These were brought into existence by people dabbling in black magic practices such as necromancy, sex magick, elemental magick, channeling, etc. They are also the agents that are employed in curses. These entities are free-agent "ghosts" which tend to have no will of their own. They can be commanded to carry out missions, but once created or empowered, they are difficult to get rid of. This is why sorcerers who dabble with these energies are frequently plagued with bad luck. Other names for Qliphoth are "homunculus" , "magickal childe", and "daemon". They do not tend to take a visible form but can be felt or "sensed". When not employed, they tend to hover around the last place where they were used, or return to their sender, vampirizing vital energy from whoever is near-by. Some people who think they have been cursed have simply attracted a stray "magickal parasite". Those who participate in seances, or play with Ouija boards are most at risk for attracting such strays. Qliphothic entities can be exorcised, but it is not easy, and the process is somewhat harrowing. Over time, if neglected, unemployed, and lacking someone to "siphon" energy from, they will eventually fade away completely.
Of the poltergeist category, I will only say a little. It is not a "ghost" manifestation per se . The moving and/or flying objects are often a result of psychic turbulence emanating from adolescent females with raging hormones. The phenomenon also manifests sometimes in the presence of adult women during menstruation. In the case of virgin girls, the cure for poltergeists is patience, as this problem goes away once the hormonal levels stabilize. For adult women, the chinese herb formula Tang Kwei Jin or something similar may cure it.
The Deity (or "Holy Ghost") category is more problematic. Often it will happen that religious feelings result when a person is moved to awe by a manifestation from one or more of the other categories. The character of that awe is the product of what I dare to call a pathological condition. To explain what I mean by that, I'll give a brief discussion of Memetics. Memetics is the study or observation of memes, which are linguistic "germs", that is to say, "viruses" encoded in and transmitted through language. Most or all concepts of a god are transmitted through written or spoken words, and thereafter all manifestations natural or supernatural are seen as emanating from the will of that "god". The brain has become reprogrammed by that thought-virus to perpetuate and spread the virus to others, just as real viruses do to DNA. DNA is one kind of code, words are another. The most powerful Deity Virus is the YHWH virus, and all of its mutations. It has endured by adapting to ever-changing demands put upon its host brains, and has even managed to influence the character of other Deity Viruses. The only way to cure an individual of an active Deity Virus is by Heroic Deprogramming, a process as brutal and harrowing to the patient as chemotherapy is to a cancer patient, and as with the latter example, likely as ineffectual, with the possibility of an eventual reinfection.
Finally, the ghost (or haunt) category. This is the true ghost. It is a localized residual traumatic psychic imprint left on the geomagnetic grid and confined to a specific area no bigger than 1-3 miles and no smaller than 1 square foot. This can manifest in many ways, such as spectres, voices, floating lights, tactile sensations, cold or hot spots, the appearance of moving objects, etc. Sometimes difficult to distinguish from many chthonic manifestations or poltergeists, it takes a sensitive and experienced ghost hunter to tell them apart. The easiest way to make the distinction is to treat any such manifestation as a ghost, and if it fails to go away, it is likely one of the other types. The method of "busting these ghosts relies on effectively de-anchoring them from the geomagnetic grid. When effectively de-anchored, they will inevitably fall back into the "void of potentiality", what some people refer to as "the source" or "the light". De-anchoring them requires courage and a willingness to accept that a mistake could cost you your life or sanity. The only ghost-hunter I've seen represented in media that remotely approaches the correct way of doing things is the character Simon Iff, a paranormal detective created by Aleister Crowley. Historically, the most fearless and effective ghost hunters have been Taoist magicians, who for many centuries have been refining the art. Taoist magicians are immune to the Deity Viruses, and for that reason have been free from distraction to carry out their work. Applying the principles of Geomancy (feng shui) as well as other more esoteric arts, they can easily rid a space of ghosts, and (temporarily) even chthonic entities. I may venture to say that the Taoist approach, if it is mastered, can readily eliminate or prevent manifestations from all five categories. Further, a Taoist magician can create or redirect these manifestations to serve good or not-so-good purposes. The modern ghost hunter must have a familiarity with the Taoist principles, as well as various more recent findings, such as the "law of the trapezoid". A thorough familiarity with occultism and folklore is expected, and a heightened sensitivity to subtle ambient cues (intuition). Training in shamanism (primitive spirit-retrieval art) would do you much good, too. An apprenticeship is highly recommended, as it is good to observe and learn the experience of a seasoned hunter. However, I will concede that some individuals may be gifted. I nevertheless advise younger ghost hunters to work in pairs just in case there are problems. The uniform of the professional ghost-hunter is not about cut and color, but conductivity. The ghost hunter must be well-grounded, because when approaching ghosts, you need to be equally installed in the "grid" the better to perceive them. Your footwear must be solid leather, tops, soles, and insoles, and very sturdy. No plastic, rubber, or artificial fibers. Socks should be 100% wool. No artificial fibers in your clothing either. No zippers, only buttons or buckles. Glasses or shades must be of real glass with wire or metal rims. No electronic items are to be on your person. Chronometers, if worn, should be wind-up, and kept in a pocket, rather than on the wrist. If you use any instruments to measure radiation or EM levels, put them down before aproaching your quarry. These things interfere greatly with your effectiveness. Do not wear or use crystals or any gems or precious stones unless you are 100% confident about the practical effects of bringing such things into your work. There are circumstances whereby a crystal could potentially make your quarry stronger than you. Once you have identified your ghost, moving or stationary, and ascertained that it is of the simple haunt category, you must with confidence stride right up to it and (depending on your training) either walk into it, stand on it, or take it in your arms. Momentarily, its place on the grid is also yours, and a window of opportunity opens up to de-anchor it. The Taoist approach is to open up a passage within oneself into the void whereto the ghost will quickly be drawn. If you screw up this part, guess what: You and that ghost now share the same body until you can regain your balance enough to try voiding it again. In this practice, fear is your enemy, not ghosts. Disciplined control of your rate of breath and heart beat should be automatic, as absolute equilibrium and serenity are essential to your capacity to time everything perfectly. It is difficult to anticipate what kind of sensations will be felt at the moment of contact, although it's safe to say that it's never pleasant. It may happen sometimes that you've misidentified your ghost and find yourself trying to void a qliphothic or chthonic critter. Well, all I can say is good luck to you. Some have succeeded. This is where your training really comes in handy. I've seen many failures, dead or insane from a bad encounter. If you have ID'd something that you have doubts about, go the safe route and try some feng shui on it instead. It's perfectly okay to throw your hands up and admit that you can't handle something.
In some countries, professional ghost-hunters are welcome and appreciated parts of a community, as they are often by trade also shamans, healers and wise counsellors. However, here in the Western hemisphere, the true professional ghost-hunters work underground. Absolutely shunning media attention, they get clients solely by word-of-mouth, and will literally "enforce" the secrecy clause in their contracts (and not in court, mind you). It is too easy to create a media circus around these things, and the next thing you know, there are laws, licenses, mail-order schools, and fee regulations. We don't want that, and thus the strict protection of our art. Most high-profile ghost-hunters that one sees in books, magazines, and on television, are not of this discipline, but are merely common attention-starved thrill-seekers who simply want to see ghosts and document them, but lack the means to remove them. In conclusion, I would like to comment that these five categories are only categories for the convenience of classification. In reality, there are hybrids as well as certain anomalies which lie outside these five that I have named. I also do not accept responsibility for the consequences arising from individuals undertaking to hunt ghosts solely on the information found in this essay. :)