"Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you" (Matthew 28:19-20).
Baptism is one of two sacraments in Protestant theology; the other being Communion.
Our Lord commanded that we be baptized. Baptism is an outward sign of an inward change. It is a response to having received salvation through Jesus Christ. Baptism does not save; it is a result of salvation.
As circumcision was a sign of the Old Covenant, so baptism is a sign of the New Covenant. It symbolizes our death, burial, and resurrection through Jesus Christ. "Don't you know that all of us who were baptized into Christ Jesus were baptized into his death? We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life" (Romans 6:3-4).
Baptism also symbolizes the sanctifying work of the Holy Spirit in our lives: "He saved us through the washing of rebirth and renewal by the Holy Spirit, whom he poured out on us generously through Jesus Christ our Savior" (Titus 3:5-6).
There are some conflicting opinions as to the proper method of baptism, just as there are conflicting opinions as to who should be baptized. Some believe baptism should be by immersion, while others believe that sprinkling is proper. Some believe that only those who have made a personal confession of Christ should be baptized, while others believe that infants of believing parents should be baptized also. These points may be debated, but should not be reasons for breaking fellowship. What is most important is that we honor Christ's command.
Some cults teach that baptism, to be legitimate, must follow a specific formula. Some teach that it must be done by the "true Church," which in their opinion means their church. As is the case with all cults, these groups mistranslate Scripture, and take verses out of context in order to "prove" their case. For them baptism becomes a means of achieving salvation -- it is a doctrine of salvation by works. True Christian baptism is a response to having received salvation, and is never a method by which salvation is achieved.