The origin and foundation of Christian Baptism is Jesus. Before starting his public ministry, Jesus submitted himself to the baptism given by John the Baptist. The waters did not purify him; he cleansed the waters. . . . Jesus did not need to be baptized because he was totally faithful to the will of his Father and free from sin. However, he wanted to show his solidarity with human beings in order to reconcile them to the Father. By commanding his disciples to baptize all nations, he established the means by which people would die to sin – Original and actual – and begin to live a new life with God.
In Baptism, the Holy Spirit moves us to answer Christ's call to holiness. In Baptism, we are asked to walk by the light of Christ and to trust in his wisdom. We are invited to submit our hearts to Christ with ever deeper love. ~from the United States Catholic Catechism for Adults
For adults today, the Church, after the Second Vatican Council, has restored the order of the Catechumenate in the Rite of Christian Initiation of Adults. It outlines the steps for the formation of catechumens, bringing their conversion to the faith to a greater maturity. It helps them respond more deeply to God's gracious initiative in their lives and prepares them for union with the Church community. This process is meant to form them into the fullness of the Christian life and to become disciples of Jesus, their teacher.
For youth and adults who are 7 years and older: Preparation for both youth and adults baptisms is intentional. Children, teenagers, and adults over 7 years who wish to be baptized need to complete the Order of Christian Initiation for Adults (OCIA) or the Order of Christian Initiation of Children (OCIC), where they will receive all the Sacraments of Initiation at the Easter Vigil (Baptism, Confirmation and First Communion).
For infants or children under 7 years: Parents and their selected godparents who wish to baptize their infant or child under 7 years will need to prepare through the parish's baptism seminar classes.