Concerning the Planes

Demonology has been a study that humanity has been interested in since the dawn of the written word. Even in formal literature as early as Christopher Marlowe's Doctor Faustus (1604?) has the image of a mortal making a pact with the devil been of intrigue. A great many informal tales, passed down by legend and word of mouth, have pre-dated Faustus while still communicating the same idea -- that humans can control the supernatural.
The means to this control has always been a sordid issue. After all, how does one say definitively that there is only one way to do such a thing, or that any one way is better than another? It is a hard task, to say the least. There are many methods available, but the most popular ones of the current age come from four sources: The Keys of Solomon, The Sacred Magic of Abramelin the Mage, Satanism and Folk Demonomancy.
The Keys of Solomon suggest an approach which both honours the demonic realm and which acknowledges the superiority of God over demons, thereby logically making the extension to use Him as a mechanism to control the hellspawn. The Keys of Solomon suggest elaborate rituals in the "Greater Keys" (the first three books of the eight book series). These rituals involve a large amount of moral, physical and spiritual preparation, magical tools, and precise incantations intoned at the correct times. It is a fairly complex and involved system, but it has survived so long only because it works. The bottom line is that, despite consuming resources, it is the longest standing and most reliable manual on conjuration available.
The Sacred Magic of Abramelin the Mage is another old collection of tomes used for a variety of reasons. Some of these reasons are to control the spirits of earth to obey the Conjurer's bidding. Here is the breakdown of this three-book collection as stated by S. L. MacGregor Mathers (a noted translator of magical texts) on page six of the first book:
First Book: = Advice and Autobiography; both addressed by the Author to his son Lamech. Second Book: = General and complete description of the means of obtaining the Magical Powers desired. Third Book: = The application of these Powers to produce an immense number of Magical results.
As with The Keys of Solomon, The Sacred Magic of Abramelin the Mage comes from a Jewish mystical tradition aimed at the personal purity of a potential Conjurer. It suggests rituals intended to keep the Conjurer pure so that the evil of demons cannot take hold of whoever may conjure them. I mention this point only to bring it to you attention, to highlight its contrast with the next two methods of conjuring.
Satanism also, as one might guess from the name, has a hand in the manipulation of demons. The method of protection, in this case, is radically different from that used in the Jewish conjuration systems. The theory in this method is that humans and demons are on the same side -- that of being anti-God and pro-hedonist. Demons are also, in this view, merely manifestations of the mind, like Freudian "ego" given form and let loose to roam the earth. As such, Satanic conjuration rituals involve the invocation of many ancient gods and entities to oversee that a desire is met. In exchange, some sort of trade is made. A payment is made to the gods responsible for fulfilling a Satanic spell in the form of food, drink, money, or some other tangible offering. Ocassionally, a non-tangible thing, such as your health, can be used as a swap item for these demonic trades, although trades of this nature are generally unacceptable in Satanic conjurations and fall more appropriately into the "Folk Demonomancy" class. The requirements change, of couse, in accordance with which gods fulfilled the request.
Folk Demonomancy is the final method used in the modern age. This type of conjuration has no cut-and-dry rules of what to do or not do, since it varies with each practitioners beliefs and practices. Typically it adheres to a Faustian barter system, not unlike the Satanist. The difference is what gets bartered. Your soul is the classical trade item for a conjuration made with Folk Demonomancy. In exchange for some earthly pleasure, the Conjurer usually offers the souls of X amount of others. If X amount cannot be obtained by the agreed date ("obtained" usually means making X amount of other people enter into a pact of their own with one or more demons), the Conjurer's own soul is forfeit and their life is taken as a security. The Faustian deal, however, is only half of what can be classed as Folk Demonomancy. The other half is similar to the methods of a Sorcerer. In this second variation, the Conjurer is kept totally secured from the demons that are used through the application of sigils, symbols, magical ingredients, protection spells, amulets, talismans, and whatever else can be mustered to resist the maelstrom of a demon's entrance to the physical plane. This mish-mash has had mixed results throughout history, with some being recorded as complete successes, and others ending in utter chaos and bloodshed.
Given the vast array of possibilities for the Conjurer, the only constant is that one must study. Each of these methods involve a great deal of thought, time, effort, concentration, patience, and wisdom. The Conjurer must immerse themselves in the study of Demonology until they are fully equipped to grapple with the unseen evil in the ethereal atmosphere and bend it to their will.