Inscription in the forecourt of the Temple of Apollo at Delphi.
Centuries before the birth of Christ, devout pilgrims made the arduous trek to Delphi to ask for advice from the famous Oracle. City states made generous contributions, some even establishing treasuries on the site. For more than six centuries, until the shrine was destroyed by the Christian emperor Arcadius in 398 CE, Delphi truly shaped the history of the world.
The original story is that long ago, a shepherd named Kouretas noticed his goats acting very strangely near a certain opening in the earth. He told his neighbors about it. Some of the curious investigated the fumes, went into trance, and began to mumble prophecies. This went on until a few rash individuals overdid it, got carried away while in trance and, temporarily insane, killed themselves by jumping into the opening. Someone, probably a village official or a priestess of the Earth Goddess religion, appointed a woman to serve as the official sibyl, or oracle. A tripod was rigged over the fissure to provide a bit of security, and more permanent buildings followed: a shrine to the goddess, a house for the sibyl, and so on.
Word of the Oracle spread fast. After the takeover by the followers of Apollo, people traveled to Delphi not only from other areas in Greece, but also from Egypt, Asia Minor, and Italy for private consultations. The economy boomed because of the number of people making the pilgrimage. Donations paid for the building of a theater and a stadium.
The Temple of Apollo was the very center and heart of the shrine, the seat of the Oracle. During the French excavation, a pool connected to an aqueduct was discovered between the Treasury of the Athenians and a portico. This pool plunged under the Temple. Perhaps that was where the Oracle ritually bathed, not in the area open to the public, as some would have it.
On the morning of a day when the Oracle was scheduled to prophesy, a goat would be sacrificed at an altar just outside of the great Temple of Apollo, and its entrails would be examined. If results were favorable, the Oracle would operate that day. She would then complete the prescribed rituals: purification in the Castalian waters, dressing in full ceremonial robes, sometimes chewing a few laurel leaves, seating herself on the tripod and inhaling the foul-smelling vapors.
Before the pilgrim entered the Temple and descended into the smoky enclosure of the Oracle, he had to make an offering. His question was written and given to one of the Oracle's assistants. Then, the pilgrim waited in a corner until an answer was recorded and delivered to him. The entire experience was surrounded by ritual and spirituality. The people truly believed that the god Apollo spoke through the Oracle, merely using her vocal cords to express his wishes and advice.
The Pythia was knowledgeable in many areas: history, religion, geography, politics, mathematics, philosophy, etc. She uttered advice on where and how to build cities, which laws to incorporate, and which prayers to utter. Her predictions were often very shrewdly phrased, which caused many supplicants to misinterpret the advice. The most famous instance of this comes down to us through a Delphic prediction given to Croesus, king of Lydia. In 550 BCE, Croesus was preparing to invade the Persian Empire when he consulted the Oracle about his chances for victory. After sacrificing 300 head of cattle to Apollo, he had gold and silver melted down into 117 bricks, which were sent to Delphi, along with jewels, statues, and a gold bowl weighing a quarter of a ton. With these gifts, Croesus sent his question of whether he should attack Persia.
The Pythia answered that, if he crossed a river, "Croesus will destroy a great empire." Encouraged by this response, he invaded Persia, only to suffer a decisive defeat. The Persians invaded and then conquered Lydia and captured Croesus, who thereafter bitterly denounced the Oracle. He sent his iron chains to Delphi with the question, "Why did you lie to me?" The Pythia correctly answered that her prophecy had been fulfilled. Croesus had destroyed a great empire -- his own.
http://www.dreamscape.com/morgana/desdemon.htm
Delphic Maxims
Know yourself.
Nothing in excess.
Aid friends.
Control anger.
Shun unjust acts.
Ackowledge sacred things.
Hold on to learning.
Praise virtue.
Avoid enemies.
Cultivate kinsmen.
Pity supplicants.
Accomplish your limit.
When you err, repent.
Consider the time.
Worship the divine.
Accept old age.
http://history.missouristate.edu/jchuchiak/ancient_greek_sayings.htm