About the Sacrament of Confirmation
"Now, when the apostles, who were in Jerusalem, had heard that Samaria had received the word of God, they sent unto them Peter and John. Who, when they were come, prayed for them that they might receive the Holy Ghost. For he was not as yet come upon any of them: but they were only baptized in the Name of the Lord Jesus. Then they laid their hands upon them: and they received the Holy Ghost." - Acts 8:14-17
"And grieve not the Holy Spirit of God: whereby you are sealed unto the day of redemption." - Ephesians 4:30
First, what is Confirmation (also called "Chrismation")? What does Confirmation do? Confirmation:
The Sacrament may only be received by one who is baptized, preferrably while he is in a state of grace (i.e., not in a state of mortal sin). If it is received when the recipient is not in a state of grace, it is illicilty but still validly received; the fruits of the Sacrament will be delayed until he receives Penance. In addition, if the confirmand (the one to be confirmed) has reached the age of reason, he should be well-catechized and know the Pater (Our Father), the Ave (Hail Mary), the Apostles' Creed, and the 10 Commandments.
The ordinary minister of Confirmation is the Bishop; priests are extraordinary ministers of the Sacrament and may offer the Sacrament if the Bishop authorizes them to. The matter is the imposition of hands, the chrism, and the annointing. The form of the Sacrament is:
"N., I sign thee with the sign + of the Cross, and I confirm thee with the chrism of salvation; in the Name of the Father + and of the Son + and of the Holy + Ghost.".
As in Baptism, a sponsor is chosen to stand for the confirmand. The sponsor should be a baptized and confirmed Catholic who's at least 14 years old, is of the same sex as the confirmand, and is well-instructed in the Faith. Also as in Baptism, among those who may not act as sponsors are: members of religious orders, spouses in respect to each other, parents in respect to their own children, infidels, heretics, members of condemned secret societies, and public sinners. The 1917 Code of Canon Law excludes godparents from being sponsors except in cases of emergency, but the 1983 Code of Canon Law recommends the opposite practice: that the godparent should act as sponsor at Confirmation if at all possible in order to better tie Baptism and Confirmation together.
In any case, just as Abram became Abraham, as Jacob became Israel, as Simon became Peter, and as Saul became Paul, the confirmand takes on the name of a Saint when he is sealed to the Holy Ghost. This isn't necessary for the sake of validity, but it is the traditional practice of the Church, and especially important for those whose Baptismal names are pagan. Read the lives of the Saints and choose your patron well!
If one is raised a Catholic, one is usually confirmed around the age of 7 or so, though Confirmation may come earlier or later at the discretion of the priest and Bishop. If a child attends a Catholic school, he may be confirmed along with classmates in preparation for First Communion together as a class. If one enters the Church as an adult, he is usually baptized (if necessary), confirmed, and offered his first Communion all at the same time (usually at the Easter Vigil), but Confirmation may take place outside of the Easter Vigil, at the discretion of the Bishop and the priest.
On a cultural note, just as in Baptism, Holy Matrimony, Holy Orders, and one's First Communion, it is customary for guests to bring a small gift to the one receiving the Sacrament, a gift usually, but not necessarily, religious in nature. Icons of his new patron, rosaries, books, etc. are typical. A small party may follow the ceremony, especially in the case of young confirmands.