A believer should be baptized in the name of the Father, Son, and Holy Spirit, just as Jesus said.
Jesus said, "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit, teaching them to observe all that I commanded you; and lo, I am with you always, even to the end of the age." (Matthew 28:19-20)
Furthermore, we need to be fully aware of what we are doing when we are baptized. If anyone was baptized as a child and didn't fully understand the gospel, that person should be baptized again, being aware of what he is doing.
Baptism is an important step in the believer's life. It means to die with Christ and rise with Christ.
Baptism in the Bible involved full body immersion into water. Being in the water is like being buried (dying to sin) and rising from the water symbolizes rising with Christ to new life.
So baptism symbolizes our dying to sin and living new life in Christ.
"Therefore we have been buried with Him through baptism into death, so that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life. For if we have become united with Him in the likeness of His death, certainly we shall also be in the likeness of His resurrection, knowing this, that our old self was crucified with Him, in order that our body of sin might be done away with, so that we would no longer be slaves to sin; for he who has died is freed from sin." (Romans 6:4-7)
If a person is able to be baptized while living on earth, then he should be baptized.
Baptism gives glory to God and testimony to people that you are His.