According to the Catholic Encyclopedia, here's the history and rituals of the papal conclave:The conclave rules were implemented in the 13th century, after the choice of Gregory X took nearly 3 years.
The early rules of the conclave were very stringent, requiring, among other things: After the pope's death, the cardinals were to wait 10 days for others to a arrive; all were to assemble near palace where pope died in one room, without partition, and live in common; the room was to be closed off so no one could secretly come and go; no messages could be sent; a window could allow food to be passed into the room; food rations were to be cut if the cardinals did not arrive at a decision within three days; after five days they would only be given bread, wine and water.
These rules have been eased over the centuries.
Upon the death of the pope, the cardinal camerlengo strikes the forehead of the dead pope three times with a silver mallet.
The pope's ring and seals are broken.
Legal evidence is drawn up attesting to the pope's death.
In this initial, nine-day period, all cardinals wear uncovered vestments to show that "supreme authority is in the hands of the whole College."
A conclave, strictly speaking, is a large room in the Vatican palace that is walled off with space divided into apartments.
Each apartment contains a crucifix, a bed, a table and a few chairs.
Four openings allow for the passage of food and other necessities, and each is guarded.
A single door provides access to the conclave.
The door to the conclave is closed until the election is announced.
However, a cardinal who is late to the conclave will be allowed in.
Communication with the outside is forbidden.
Loss of office or excommunication are the punishments for violating this rule.
The cardinals in the conclave live in the apartments. Each apartment is covered with a cloth.
Meals are served in common, but eaten in private, and written communication is forbidden.
The conclave officially opens officially on the 10th day after the pope's death. The morning of this day, the cardinals assemble for a Mass in the Pauline Chapel.
After the Mass, they assemble in the Sistine Chapel, where the voting takes place.
Six lighted candles are placed on the altar. The altar also bears the chalice used in the voting.
Each chair sits before a writing desk, and the conclavists bring writing materials with them into the Sistine Chapel.
The standard form used for the vote is called a "scrutinium," or secret ballot.
A two-thirds vote is required to win election.
When a cardinal places his vote in the chalice, he takes this oath: "I call to witness the Lord Christ, Who will be my judge, that I am electing the one whom according to God I think ought to be elected."
If no one receives two-thirds of the vote the first time around, there is a second vote in which the conclavists can change their decisions.
When the required two-thirds vote is not obtained, the ballots are placed in a stove. The chimney of this stove exits through a window of the Sistine Chapel.
When there is no election, straw mixed into the ballots to produce a thick smoke (sfumata) that indicates to those waiting outside that there has been no election.
Each day, a vote is taken in the morning and in the evening.
When a candidate has been elected, the cardinal dean asks him whether he will accept and which name he wishes to go by as pope.
This is in imitation of St. Peter's change of name.
The successful candidate is immediately placed in the papal garments, and the Fisherman's Ring is placed on his finger.
A proclamation is made to the people from St. Peter's, and the conclave disperses.