Why be Baptised
The bible tells us that when we become a Christian we need to be baptised.
If you don't know that you are a Christian, then you need to read
How to be a Follower of Jesus Christ
This is not referring to infant baptism or "christening". Baptism is something that comes after you have been saved.
"As many of us as were baptized into Jesus Christ were baptized into His death. Therefore we were buried with Him by baptism into death, so that as Christ was raised up from the dead by the glory of the Father; even so we also should walk in newness of life. For if we have been joined together in the likeness of His death, we shall also be in the likeness of His resurrection (Romans 6:3-5)"
The bible teaches that the act of baptism symbolises our association with Jesus Christ in His death, burial and resurrection.
It was by the will of God that Jesus Christ was crucified (and thereby paid the penalty for our sin). It was by the power of God that Jesus Christ was resurrected to new life. In effect, when we are saved God works a similar miracle in our lives - the change is that profound.
Baptism represents that death and miraculous new life. By being baptised we are giving witness or testimony of what God has done for us.