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.
Preparation for both adult and child baptisms is intentional. Adults and youth who wish to be baptized need to complete the Rite of Christian Initiation, and parents who wish to baptize their baby will need to prepare through the parish's baptism seminar classes.