Hi, Olivia! Thanks for your question; I hope we can answer it satisfactorily!
Baptism is one of the ordinances in the Baptist church (the other being the Lord's supper, or communion). An ordinance differs from the sacraments of the Catholic church in that a sacrament by definition is believed to impart saving grace, whereas an ordinance (something ordained) is something that God has commanded us to observe, as a point of obedience.
The Bible says in Ephesians 2:8-9, "For by grace ye are saved through faith; and that not of yourselves: it is the gift of God: not of works, lest any man should boast." Romans 10:8b-10 says: "...that is, the word of faith, which we preach; That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. For the scripture saith, Whosoever believeth on him shall not be ashamed. For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. For whosoever shall call upon the name of the Lord shall be saved."
Because of these verses, we believe that salvation cannot be earned by works of righteousness, sacraments, or anything similar. Salvation occurs when a person trusts that Christ has completely taken the punishment for their sins when He died on the cross (Romans 5:8), believes He is Who the Bible says He is (the perfect, sinless Son of God who died and rose again from the dead [John 1:29]), and stops trusting their own works to earn them righteousness (Titus 3:5). When a person so trusts Christ, God will, by His grace, freely give them salvation (John 3:16). Thus, baptism cannot bring salvation, and is not necessary to be accepted by God. We baptize because God commanded it (as an ordinance), and it is the first step of obedience for a new believer to do after they receive salvation. This is why we baptize people when they are older, and not babies. Babies are too little to choose to trust Christ in such a manner.
Baptism is a picture of what Christ did for us - he died, was buried, and rose again - and the Bible says that God identifies us (in a spiritual sense) with what Christ has done for us. Colossians 2 talks about this, and I would encourage you to read it for better understanding.
This view is reinforced by 1 Peter 3:21. This says: "The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ." This verse is a little confusing because of the word 'save', which we usually take to refer to salvation from hell. It's actually talking about a different kind of saving - and we can see that by the verse itself, which tells us that baptism does not 'put away the filth of the flesh', but is 'the answer of a good conscience toward God.
We baptize by immersion for a couple of reasons. One, the original Greek word "baptizeo" means "to immerse". Secondly, Jesus was baptized by immersion in the Jordan. Thirdly, and most importantly, baptism by immersion pictures the death, burial and resurrection of Jesus Christ. What happens when someone dies? We bury them. We don't just sprinkle some dirt on their head.
Now, as far as the ceremony... well, it requires water. Lots of it. Details may vary by congregation, but there are several basic parts that are always present. Since baptism must follow salvation, the pastor will ask the person being baptized to share their testimony with the congregation. The pastor has probably already heard the testimony, as there are often classes offered before the baptism ceremony to teach and ensure that the participants understand what they are about to do, but the testimony is shared publicly as baptism is to be a public testimony of one's faith in Jesus Christ. Once the individual and the pastor are in the water, they will get in position for the baptism (this often involves crossing the arms to give the pastor a good place to grasp & holding one's nose, while the pastor braces himself to lower and lift the person into and out of the water). They are then baptized "in the name of the Father, Son, & Holy Ghost." In my church, while lowering the person into the water, my pastor would say something like this: "Upon your confession of faith in Jesus Christ, I baptize you, my (brother/sister), in the name of the Father, Son & Holy Ghost. Buried in the likeness of His death; raised in the likeness of His resurrection." Then we'll often sing a hymn as a congregation to give them a chance to get changed into dry clothes. There are no special symbols/colors shown. Baptism itself is the important symbol, picturing as it does the work of salvation that Christ has already finished! That's why He said, when He died, "It is finished." Everything necessary for our salvation was completed. No more sacrifices, masses, works, or anything is required - and indeed - if we trust such 'works of righteousness' to help earn us salvation, then we are not trusting Christ alone as our Savior. And it is only when we trust Christ alone that God will give us His salvation.
Hebrews 10:10-15 "By the which will we are sanctified through the offering of the body of Jesus Christ once for all. And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins: But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God; From henceforth expecting till his enemies be made his footstool. For by one offering he hath perfected for ever them that are sanctified."
Best of wishes on your assignment!