Baptism is the removal of the stain of original sin and becoming a Christian, a son or daughter of God the Father.
Baptism. God's saving grace, His very presence, enters into the human soul. The essential rite of baptism is very simple. The person celebrating the sacrament (usually a priest or deacon) says 'I baptize you in the Name of the Father, and of the Son, and of the Holy Spirit' while pouring water over the head of the person receiving the sacrament or dipping the person in water. For Catholics, baptism is the sacrament of salvation and the door to all other sacraments.
Baptism forgives all personal sin, takes away original sin (but leaves concupiscence, a tendency toward or desire to sin, and the other effects of original sin like death, disease and a darkened intellect), infuses sanctifying grace, and is necessary for salvation. Baptism imprints in the soul a character, a certain spiritual and indelible sign, and so can only be received validly once. Persons of any age may be baptized, from infant to adult. Only the baptized may receive the other Sacraments. The grace received by baptism may be lost by the commission of an actual mortal sin.
How to pick Godparents: Dear mothers and fathers preparing for the birth of a child, congratulations! The Church shares your joy! As you prepare for the birth of your child, and as you prepare for the baptism of your child, please keep the following Requirements for a Godparent in mind as you choose a Godparent for your child. First of all, a Godparent helps the baptized person to lead a Christian life in keeping with baptism and to fulfill faithfully the obligations inherent in it. With this in mind, please remember that you can choose to either have ONE Godfather or ONE Godmother, or one of each. The Catholic Church does not permit there to be more than two godparents. According to Church Law, those to be chosen as a Godparent must be a Catholic who is at least 16 years old and who has been confirmed and has already received the most holy sacrament of the Eucharist and who leads a life of faith in keeping with the function to be taken on. This means that if they are married, their marriage must be recognized by the Catholic Church. Provided that there is at least one Godparent, a baptized person who belongs to a non-Catholic denomination may serve as a witness to the baptism. Catholics who do not meet the requirements to be a Godparent can NOT serve as a "Christian witness".
Emergency Baptism An emergency baptism means that the normal rites are not employed, but owing to necessity the minister (priest, deacon or even a lay person), baptizes someone desiring to be baptized, or a child before the age of reason who is dying, using only the necessary form ("I baptize you in the name of the Father, and of the Son and of the Holy Spirit.") A priest having the Sacred Chrism oil with him would also confirm the person if in serious danger of death. Ordinary water may be used for emergency baptism, though holy water is preferred if available. One could baptize conditionally with doubtful matter IF that was indeed all there was available and time was of the essence. For certain validity the water should be poured sufficiently so as to run, three times, over the forehead (if accessible), the head, other than on the hair, if not. The words should be spoken, even if inaudible to others, and not just said mentally. The Church has not ruled on such details, but the common teaching of theologians over the centuries should be followed. It would be presumptuous and dangerous to souls not to do so.
While children may not be baptized contrary to the will of the parents, except in danger of death (it's God's will expressed through the Church), an adult may never be baptized without an indication that this is his or her will. It would be in vain to do so, and an abuse of the sacrament. This would be objectively sinful, though you obviously are unaware of that fact and so are excused. The adult person to be baptized must have expressed their will in some way, and if opportunity affords given the minimum catechesis - God, Christ, Heaven (reward), Hell (punishment).
Baptism is not a private matter, and so should be reported to the pastor of the parish in which it occurs. Non-Ordained are high discouraged to baptism even in emergency unless it is clear there is not a priest or deacon available.
For information on the preparing for your child's Baptism in our AFC, see the Baptism preparation page.