Who should be baptized? Believers - (Acts 10:43-48) "To Him all the prophets witness that, through His name, whoever believes in Him will receive remission of sins." While Peter was still speaking these words, the Holy Spirit fell upon all those who heard the word. And those of the circumcision who believed were astonished, as many as came with Peter, because the gift of the Holy Spirit had been poured out on the Gentiles also. For they heard them speak with tongues and magnify God.
Then Peter answered, “Can anyone forbid water, that these should not be baptized who have received the Holy Spirit just as we have?” And he commanded them to be baptized in the name of the Lord. Then they asked him to stay a few days.
Why should we be baptized? Obedience - (Matthew 28:17-20) When they saw Him, they worshiped Him; but some doubted. And Jesus came and spoke to them, saying, “All authority has been given to Me in heaven and on earth. Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age.” Amen.
What mode of baptism should be used? Immersion - (Mark 1:9-11) It came to pass in those days that Jesus came from Nazareth of Galilee, and was baptized by John in the Jordan. And immediately, coming up from the water, He saw the heavens parting and the Spirit descending upon Him like a dove. Then a voice came from heaven, “You are My beloved Son, in whom I am well pleased.”
What is the meaning of baptism? Identification with Christ - (Romans 6:1-11) What shall we say then? Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin live any longer in it? Or do you not know that as many of us as were baptized into Christ Jesus were baptized into His death? 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. For if we have been united together in the likeness of His death, certainly we also shall be in the likeness of His resurrection, knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin. For he who has died has been freed from sin. Now if we died with Christ, we believe that we shall also live with Him, knowing that Christ, having been raised from the dead, dies no more. Death no longer has dominion over Him. For the death that He died, He died to sin once for all; but the life that He lives, He lives to God. Likewise you also, reckon yourselves to be dead indeed to sin, but alive to God in Christ Jesus our Lord.