Across the millennia, there have been many who have sought to see the future, perceive hidden information, and so on. Some did this through the working of magic, others by calling on spirits or gods, meditating, or reading between the lines of holy books. Then, there are a large number of other highly diverse and discrete methods, collectively referred to as divination.
At this point it should be noted that, in almost all cases, the message is little more than a kind of Rorschach inkblot1, and whether it comes true or not (and indeed, how it does) all depends on the will and perception of the diviner. For example, suppose someone 'saw' that they would come into money. This 'prophecy' could be fulfilled by simply finding a few coins on the ground, or even seeing some poor people and realising that one is actually quite well off after all. The author takes no responsibility for predictions that turn out wildly inaccurate from what is expected.
Believers ascertain that there are four main types of divination: omen, pattern, symbol, and trance. Omen divination refers to reading signs that are naturally present, pattern divination involves creating a shape and interpreting it by fixed guidelines, symbol divination involves such things as the I Ching and Tarot, while trance divination requires entry into trance states, perhaps aided by a little LSD.
There are many forms of omen divination; indeed, it could be said that there is an infinite amount, since they all largely revolve around reading prophecy from apparently random natural occurrences. For example, people can and do read hidden meanings in the shapes of trees, the way wood burns, the migratory patterns of birds, cloud shapes, etc.
In both the modern and ancient worlds, the most popular form of divination has always been astrology. This is a very complex art which seeks to determine a person's personality from the positions of the stars, planets, sun, and moon, and occasionally asteroids relative to Earth at the moment of birth. Some astrologers have suggested looking at the skies at the moment of conception instead, but this idea has not caught on due to the fact that, in astrological theory, one must know the precise moment of birth to within about thirty seconds for any accuracy; it is simply not possible to be this accurate with conception. Some people also attempt to use astrology to answer questions, looking at the sky at the exact moment the question was asked in order to find their answer. Professional astrologers readily assert that they cannot predict the future; the best they claim to be able to do is forecast future psychological influences in a person's life.
Like omen divination, there are many different forms and ideas of pattern divination. The most well-known would be radiesthesia, though this is not a form in itself; it is a collection of similar methods. For example, there is automatic writing which is usually done with a ouija board or planchette. Automatic writing is frowned upon by most religious workers. The scientific explanation is that the writing is produced by nothing more than tiny subconscious twitches which are nonetheless enough to move the ouija board (or whatever). While automatic writing does not seem supernatural, there is a fair amount of anecdotal evidence that bad stuff often follows as a result. Therefore, the reader is advised to treat all forms of automatic writing with utmost suspicion and scepticism.
There are also other forms of radiesthesia and pattern divination. Scrying refers to looking into a clear or reflective surface such as water, glass, or crystals, and seeing images of past, present, or future events within. This is the method Nostradamus is believed to have used.
Then there are practices such as dowsing, which seeks water or precious minerals with special rods; austromancy, which uses wands; and many others. At one point, scientific experiments suggested that there may actually have been some truth to dowsing after all; however, more recent experiments have shown that this is in fact not the case.
The most well-known and popular form of symbol divination is the use of the tarot deck. Tarot cards were the forerunner to modern playing cards, and many modern diviners treat ordinary cards with the same respect as tarot cards. What sets the tarot deck apart from the everyday deck is the fact that the tarot deck has an extra picture card in each suit as well as 22 special numbered trumps, from 0 to XXI and with names such as the magician, the wheel of fortune, the pope, etc. These are said to have special properties above and beyond the 56 'small cards'. Whatever deck is used, the process is the same. The cards are shuffled, then laid out face-down in a specific way; as they are turned up, the future is revealed.
It is a common myth that the tarot deck originated in Ancient Egypt and the word tarot comes from the Egyptian tar rosh, meaning 'royal road'. Actually, tar and rosh do not appear in the Egyptian language at all; the Ancient Egyptian words for 'royal' and 'road' are in fact nesew and wethret respectively. The words tarot originated as a contraction of tarrocchi, a medieval Italian word for gambling.
Another popular method of symbol divination is the I Ching, a system which originated in China and works by tossing sticks in a particular manner; they way in which they fall is said to reveal the future, or one's true path, or whatever. Aleister Crowley is believed to have been quite fond of using the I Ching.
The shapes of people's bodies have long been believed to harbour hidden information about their personality. For example, there is the art of palmistry, which reads information from the lines of a person's hand; phrenology, nowadays slangily referred to as 'bumpology,' concerns itself with the shape of one's head; and physiognomy combines these two as it looks at the whole body to glean the desired information. One Timothy Burr even claimed that a woman's personality could be determined by the size, shape, and other qualities of her breasts.
Bibliomancy is a system of divination which works by asking a question, opening a book at random, and reading a passage. It is hoped that this passage contains the relevant answer. The Bible has long been a favourite book for bibliomancy, as well as other holy books; the logic here is that any answer contained in sacred texts cannot possibly be evil. A related art, cledonomancy, works by asking a question and taking the first thing one hears as the answer.
Nowadays, small, thick books called The Book of Answers can be bought in most bookshops. Each page of these is printed with a vague answer to some imaginary question, and may have references to tarot cards or tea leaves. They detail elaborate conditions for proper use, but even if you believe in bibliomancy, this is unnecessary; any book will do.
Also, there is geomancy, a form of divination which works by making small random holes in the ground and interpreting the shapes; arithmology, which investigates mystical properties on numbers; and arithmancy, popularly known as numerology, which seeks arithmoliogical symbolism in names, dates, etc.
Trance divination is any attempt to contact spirits or gods and ask them the answer to some question. Shamans from around the world have practised it for thousands of years, and those alive nowadays have very clear ideas as to what works and what does not. The general way of entering a trance is by altering the brain chemistry through fasting, epilepsy, or the use of certain hallucinogenic drugs. These trances often have negative side effects, even if the shaman (or would-be shaman) is extremely strong and careful; whether this is the result of angry ghosts or dangerous chemicals, it is not advisable to enter a trance unless in the presence of numerous properly-trained and experienced professionals. Trances may be used as a form of scrying without the use of physical aids.
A common form of trance use is in hypnotism, whereby the subject is pulled into a state which resembles sleep. This allows their subconscious to impart information that the hypnotised person remembers, but cannot recall. Hypnotism is frequently used to remember past lives or alien abductions.
Contrary to popular belief and fantasy literature, necromancy is nothing more than a form of divination which seeks aid from the spirits of the dead. Necromancy has nothing to do with raising corpses; it is more accurate to refer to this as goetia2. Necromancers often make use of automatic writing implements as well as trance states. Necromancy is frowned upon by the majority of both religious leaders and magicians.
The study of divination is quite interesting. Sources run the gamut from local folklore and old wives' tales to the most advanced and secretive esoteric mysticism. People's thirst for knowledge seems pretty much unquenchable. However, many attempts to predict the future necessarily run contrary to free will. While an open mind is generally a good thing, prudence is also useful when considering both making predictions and accepting them.