The process by which someone becomes Catholic is called "The Order of Christian Initiation for Adults" (OCIA)
OCIA is about a relationship. Think of it as dating the Catholic Church.
The first stage is called "inquiry" and its title is self explanatory. It is a stage where anyone can come and ask questions of the Church and learn about the basics without any commitment. Once someone discerns that they would like to take a step in seriously discerning the Catholic Church, they move on to the next stage.
The goal of the journey is to give a total, free, faithful, and fruitful "yes!" to enter into a lifelong relationship with Jesus and His Catholic Church. Therefore, it is important that the candidate and the Church get to know each other. What does the Catholic Church believe? How does the Catholic Church worship? How do members of the Catholic Church live? OCIA is a process of learning and pondering these aspects of the Catholic Church. The OCIA journey is divided into four periods (Inquiry, Catechumenate, Purification & Enlightenment, and Mystagogy) that respect the individual's journey of faith. If the individual discerns at the end of each period that he wants to move forward, he is received into the Catholic Church on the night before Easter in a liturgy of great celebration!