The decision to be baptized is a personal and a special decision. Being baptized is one of the most important steps in a Christian's life. Baptism does not SAVE YOU! Once you profess your belief, submission to Christ, and accept Christ as your personal savior by reciting your salvation prayer you are saved...period. Baptism indicates a few things...
The end of a previous life / lifestyle
The beginning of a new life / lifestyle (Born Again)
The beginning of your ministry
The End of a Previous Life
Romans 6:1 - 6 NKJV (1) What shall we say then? Shall we continue in sin that grace may abound? (2) Certainly not! How shall we who died to sin live any longer in it? (3) Or do you not know that as many of us as were baptized into Christ Jesus were baptized into His death? (4) Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life. (5) For if we have been united together in the likeness of His death, certainly we also shall be in the likeness of His resurrection, (6) knowing this, that our old man (and woman) was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin.
When you are baptized you end the previous life that you were living. In a sense you have died of yourself. This means that you will no longer think of the previous things as the most important things in your life. You being submerged below the water symbolizes death.
The Beginning of a New Life / Being Born Again
John 3:1 - 8 NKJV (1) There was a man of the Pharisees named Nicodemus, a ruler of the Jews. (2) This man came to Jesus by night and said to Him, "Rabbi, we know that You are a teacher come from God; for no one can do these signs that You do unless God is with him." (3) Jesus answered and said to him, "Most assuredly, I say to you, unless one is born again, he (or she ) cannot see the kingdom of God." (4) Nicodemus said to Him, "How can a man be born when he is old? Can he enter a second time into his mother's womb and be born?" (5) Jesus answered, "Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. (6) That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. (7) Do not marvel that I said to you, 'You must be born again.' (8) The wind blows where it wishes, and you hear the sound of it, but cannot tell where it comes from and where it goes. So is everyone who is born of the Spirit."
When you are baptized and are lifted above the surface of the water this signifies a rebirth. This rebirth is a symbolic act of a newness of life that is also referred to as being "Born Again". The important things of your life are Christ related. As you progress as a Christian ALL things of your life should be conformed to Christ's standards.
Our Savior was Baptized
Luke 3:21 - 23 NKJV (21) When all the people were baptized, it came to pass that Jesus also was baptized; and while He prayed, the heaven was opened. (22) And the Holy Spirit descended in bodily form like a dove upon Him, and a voice came from heaven which said, "You are My beloved Son; in You I am well pleased." (23) Now Jesus Himself began His ministry at about thirty years of age, being (as was supposed) the son of Joseph, the son of Heli,..
The Beginning of YOUR Ministry
When people hear the word "Ministry" they think of a formal minister or pastor. Ministry is an action or actions. We as Christians are "ministers" for Christ. - Minister defined : to give aid or service (Merriam Webster Dictionary) We as Christians in our new lifestyle"give aid or service" in the name of Christ to others. This is not about preaching but we do look to share the word of God throughout our days. Ministering is also doing (providing) for others in need.
During a baptism certain things will take place and certain requirements must be met. The link below will explain the typical requirements someone must have to be baptized and what will most likely take place during the baptism.