So, how does one become a Christian? The New Testament documents have a variety of ways of describing this. In some the Gospels Jesus calls people to follow him (e.g. Matt 4:19; 8:22, 9:9). Those that did gained entry into the Kingdom of God and salvation. To follow means to acknowledge Jesus as King or Lord and then to live by his teaching.
After Jesus died and rose through the books of Acts and the letters it is 'faith' that saves us. A great example of this is when the Philippian jailor asks Paul, 'what must I do to be saved?' Paul responds, 'Believe in the Lord Jesus Christ and you will be saved.' Faith or to believe is to accept Jesus, to believe in Jesus and all he is, has done and does. It is belief in him as saviour, that his death and resurrection saves us. It is acceptance of him as Lord, and so we seek to obey him and live his way for our lives.
What doesn't save us in the New Testament is our works. Eph 2:8-9 tells us, 'For it is by grace you have been saved, through faith —and this is not from yourselves, it is the gift of God— not by works, so that no one can boast.' This tells us that we are saved by God's gift (grace) and that all we do is believe. We can do nothing to save ourselves because we are corrupted by sin, even in our best moments. So God offers to save us, if we say 'yes' to his offer. We simply accept what Jesus has done. Faith is accepting Jesus that first time as saviour and Lord and then living every day out of trust in him. It involves that commitment to follow, and trust in him. It is really simply saying 'yes' to God's wonderful free offer of eternal relationship with him.
We don't become a Christian by obeying a religion, going to church, praying a certain way, following a particular church leader, doing good things. These all have value to grow in our faith. However, they do not save us. Jesus is the only one who can save us. He died on a cross in our place taking our sin on himself so that we would not have to face eternal destruction which all evil and sin will receive. He conquered evil and sin by rising from death. He offers to take us through to salvation with him if we accept him and what he has done.
So if you believe that Jesus is the way to salvation, all you have to do is tell God with a prayer and set out to live for Jesus. Pray something like this: 'God I acknowledge that Jesus came to save me. Thank you Jesus for dying for me in my place. I admit I am a sinful person and ask you to forgive me and to save me. Come into my life and help me to live for you. Thank you for dying for me. I commit to do my best to live for you from now on. In Jesus name. Amen.