Salvation (Christianity)

Salvation in Christianity is found through the life, death, and resurrection of Jesus. This is why Good Friday, the day the Christian churches remember His death, is called good. Also Easter celebrates His resurrection and is the most important Christian holiday. Christians believe that atonement with God was gained by Jesus for all sinners who will accept Him, as He led a perfect life.
Three Phases of Salvation.
Many Christian writers say that Jesus saves us in three ways.
Justification means that God has forgiven all our sins. This is based on Jesus having died in our place. This becomes real for any person when they put their faith in Jesus.
Sanctification means that we become people that live a good life. This process is usually gradual, but may happen quickly.
Glorification means that when we die or Jesus returns to earth we will be taken to heaven to live with him.
How Salvation happens.
Various Christian groups have somewhat different views about how salvation happens. However, all agree that the death of Jesus, followed by his resurrection is what makes salvation possible. They also agree that individual humans must respond to God's initiative. 
Before salvation can take place, a person must become aware that they need it. The Holy Spirit is God's instrument in this.
John Calvin called this Predestination, Saint Augustine and John Wesley called it "prevenient" (coming before) grace. Others call it common grace. The Catholic Encyclopedia states that salvation "begins with the grace of God which touches a sinner's heart, and calls him to repentance. This grace cannot be merited; it proceeds solely from the love and mercy of God"
A person who knows that they are in need of salvation, must also know that it is available. This happens when the person hears the gospel. The gospel is the news that Jesus has died and risen and promises eternal life to those who receive Him. The person then believes this message and responds. Various groups of Christians see this response in different ways. The Catholic and Orthodox churches, and some Restoration Churches say that the required response is Baptism. Other Protestants suggest a prayer to "ask Jesus to enter their heart (life)". In American evangelism, sometimes the suggested response has been to go to the front of a church in a public declaration of faith. St. Paul seems to have set down the proper response in his letter to the Romans, Chapter 10 verse 9. "if you confess with your mouth “Jesus is Lord” and believe in your heart that God raised him from the dead, you will be saved". Christians believe that the proper response to Jesus brings about justification, (forgiveness of sins), and begins the process of sanctification. 
Sanctification is also the work of God with the Christian responding to that work. Some churches say that the sacraments are very important in this. This would include receiving the Mass and confession. Others would emphasize reading the Bible, prayer, going to church and telling others about Jesus.