Your pastor will probably have a set of materials he will go through in preparation for the baptism. Since the early centuries, people being baptized confess the basics of the Christian teaching as summarized in the Apostle’s Creed — this includes confession Father, Son, and Holy Spirit as One God. After baptism, the new Christian has the additional promise, not based on moral behavior, performance, or feelings: “He who believes and is baptized shall be saved.” (Mark 16:16.) More on baptism.
During this time, you can offer to continue to meet with the person to talk through what he is learning in the pastor’s class, to encourage, to pray together, and to help him take first steps in growth.
If you are asked to provide the baptism preparation experience, you may consider using the Eight Lessons for New Christians, which were first written by this web’s author as baptism preparation material. In these materials, the person looks up a Bible verse and then answers a simple question. These materials include the Ten Commandments, the Apostles Creed, the sacraments, and Christian Life basics.