Why baptize?

We're baptizing believers this Sunday at somanorth. I thought it would be useful for some of you to understand the significance and reason for baptizing followers of Christ.

In the new book Believer's Baptism: Sign of the New Covenant in Christ (ed. Thomas R. Schreiner and Shawn D. Wright; Nashville: B & H, 2007), Andreas Kostenberger's Chapter argues that the Gospels teach us that baptism:

1) is designed for believers who have repented of their sin and have put their faith in God and in his Christ,
2) is an essential part of Christian discipleship,
3) is always shown to be full immersion,
4) and presupposes spiritual regeneration.

It sounds like a good read. You can buy it here.