Divination was the process of gaining insight into future or unknown events without resorting to psychic powers, trances or visions, instead employing magical tools and resources.
Users of divination did not have to possess a large amount of magical knowledge or power to divine successfully, though this could entirely depend on what method they used. For example, Jenny Calendar and Drusilla did not identify as witches, but both at one point successfully performed a method of divination (cleromancy in Jenny's case and tarot reading in Drusilla's). On the other hand, Tara Maclay, a long-time practicing witch, was unsure in her ability to read palms.
Like other forms of magic, divination could be used to contribute to the addictive effects of magic, possibly meaning that using objects like crystal balls and tarot cards drew magical energy.
Methods of Divination
Alomancy involved using salt crystals by casting them into the air and interpreting the patterns that appeared in the air or what landed on the ground. Rupert Giles tried to use this in a locator spell with Willow's help (using a sack of kitchen salt over a map surrounded by candles), but found it nonsensical. Willow reminded him that divination spells took patience and focus, something he had taught her, and it would now be trickier due to the change in universal rules.
Cleromancy involved the use of casting lots, bones and runes, allotting them and using the collected sample to make predictions.
Jenny Calendar used casting bones to predict the oncoming chaos caused by Moloch the Corrupter, an unidentified shaman was seen casting bones, allowing him to foresee the visit he would receive from Darla  and Wo-Pang, allowing him to foresee Wesley Wyndam-Pryce coming to him.
The use of tarot cards to receive instructions or messages about the future using the images displayed on the cards.
Both Tara Maclay and Willow Rosenberg owned a deck of cards. One of the psychics hired by Wolfram & Hart also was seen using tarot cards.
In 1997, Drusilla used a deck of tarot cards to predict the order in which each Tarakan assasin came after Buffy, along with finding the location of the Du Lac Cross and who was needed for the Vampire Restoration Ritual.
Willow and Tara also kept a crystal ball in their room at 1630 Revello Drive that was seemingly smashed to pieces when a demon approached them. However, it turned out it was only an illusion created by the demon when they saw that the ball was still intact. The crystal ball was eventually taken away when Willow wanted to end her magic addiction.
The art of telling another person's fortune by analyzing the lines on their palm.
Tara suggested that the Magic Box hire a real psychic to read customers' fortunes using their palms while Willow suggested that Tara could do that. Tara claimed that she wasn't skilled in palmistry but instead was interested in learning how by observing someone. Willow persuaded Tara to read from her calm, which Tara playfully read it as a "Willow hand" when asked about what she saw.
Hydromancy, or water gazing, involved gazing into special water in order to see clairvoyant visions.
Amy Madison used a bowl full of sparkling blue water to see that Buffy and her friends drowned in the sea after Twilight's army attacked. However, this vision proved to be false because in actuality, they simply descended into the seas inside a submarine. This was possibly the result of Willow's spell.
Scrying involved the use of a crystal, such a lodstone, and hovering it over a map. The crystal will be drawn to concentrations of mystical energy in the area respresented on the map.
Rupert Giles used this method to seek out Pearl and Nash in London. The stone sensed an incredible concentration of mystical energy in Hackney so much that the crystal burst into pieces on the map.
Uses in spell casting
Some methods of divination were shown to be used in the casting of some Spell. The purpose of using these methods was not necessarily a form of divining, but simply simply a step in the ritual performance. A deck of tarot cards were used in the Enjoining Spell to represent the different components in the spell (the heart, the mind, the spirit, the body), and later appeared in Willow and Buffy's dreams when they were manipulated by the First Slayer, cluing them about how the spell was the cause. The Ritual of Restoration also required the caster to cast stones for an unknown purpose.
- Scrying in reality, was used by reflective surfaces such as water, mirrors , and crystals. Well this form of Scrying might be a reference to the tv show Charmed and a divination form known as "Dowsing".