I got asked this question the other day.
Basically in a nutshell:
have resources and ask the person about what, why, where, how, when of Baptism. We talk about salvation ... that of head knowledge to heart knowledge. that God saved us by Grace .... through Faith (putting your trust in Him), Repenting (A change in mind that leads to a change in action), confessing Jesus as Lord. (We usually recite Peter's confession from Matthew 16:16 Simon Peter answered, “You are the Christ, the Son of the Living God.”) and Baptizing them (Matt. 28:19-20) by Immersing them in the death, burial, and resurrection of Christ (Romans 6 and Acts 2:38) unto Good Works.
As adults, we look at the various scriptures. Some simply state I know I need Jesus and to follow what He says ...so I need to be baptized. With children we have a little fill in the blanks, take home study to which I do with discussing with them and their parents.
Baptism is a BIG THING. It is a celebration. Unfortunately not all parents agree with it or understand it. I've had only one time where I regret baptizing a young teen without the parent's input. Lesson learned.
What lessons have you learned with doing an important thing such as a Baptism? Any regrets or misunderstandings that could of been avoided? (I remember baptizing a young man when the water heater over cooked the water --fastest baptism ever ... and apologizing ...)