1. To follow the example set by Christ.
“At that time Jesus came from Nazareth and was baptized by John in the river” (Mark 1:9) Water baptism is so important to God that Jesus himself was baptized. He modeled it for us. It’s an example that we are to follow. We are to do what He has done. So, the first reason we should be baptized is to follow the example set by Christ.
The second reason we should be baptized is because…
2. Because Jesus commands it.
Jesus Christ
commands that every Christian be baptized. “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, [20] and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.” (Matthew 28:19-20) (NIV) These three things the church is commanded to do:
A) Make disciples - help people come to know Christ
B) Baptize them
C) Help them grow up to become more like Jesus.
3. The third reason we should be 
baptized is that demonstrates that I’m a "follower of Christ" (aka: Christian).
The Bible says, “Any of the people who heard Him believed and were baptized.” Baptism doesn’t make you a Christian. It just shows that you are a Christian. It’s and outward symbol of an inward commitment. It is your commitment to Christ that saves you. Baptism just says to the world, “I’m not ashamed to tell the whole world what’s happened to me. I’ve given my life to Christ.” (Acts 18:18)
A little boy said one time, “Pastor, when can I get advertised?” That’s what baptism is. Baptism is an advertisement for Jesus. It’s saying, “i’m not ashamed of Jesus Christ.” Jesus once said, “if you’re ashamed of Me in front of the world then I’ll be ashamed of you in fro t of My Father in heaven.”