Every person who has not yet been baptized is eligible to receive baptism, according to the Code of Canon Law (CIC c. 864). For adults seeking baptism outside of emergency situations, they must express their intention, receive instruction in the faith, and complete the catechumenate process. For infants, at least one parent or guardian must consent and there must be a reasonable expectation that the child will be raised in the faith.

The determination of whether there is a well-founded hope that an infant will be brought up in the faith is ultimately left to the discretion of the minister performing the baptism. "There are no hard and fast criteria that every minister of baptism (by that I mean a deacon, priest, or bishop) follows, no checklist that says, 'these are the requirements that determine whether your hope is well founded or not.' Some ministers of baptism are more hopeful than others and might make a decision to baptize an infant that a different minister of baptism would not make."

Baptism does not have to be exclusively Catholic to be considered valid. The essential elements for any valid baptism include using real water, employing the formula "I baptize you in the name of the Father, and of the Son, and of the Holy Spirit," and intending to wash away original sin and incorporate the individual into Christian life. "Anyone who baptizes someone with the proper matter, form, and intention validly baptizes, whether the person being baptized is in full communion with the Catholic Church or not."

Regarding how water should be applied during baptism, while it is customary for water to be poured over a person's head, validity requires only that water touches some part of their body. The Congregation for the Doctrine of the Faith has clarified that hair counts as part of the body; therefore, even if water does not reach a person's scalp but touches their hair, it remains a valid baptism.