A real Christian is one who has realized that he is a sinner and can only be saved by God's grace. It is someone who has accepted Christ's sacrifice on the cross as the payment for his sins and who realizes that he cannot work his way to heaven.
Romans 3:10 "As it is written: 'there is no-one righteous, not even one'"
Romans 3:23 "For all have sinned and fall short of the glory of God."
Nobody is perfect. All of us have done something wrong in our lives. We cannot earn heaven by our own works. Earning salvation is like trying to swim from California to Hawaii. Not even the best Olympic swimmer could make the trip.
Romans 5:12 " Therefore, just as sin entered the world through one man, and death through sin; and in this way death came to all men, because all sinned."
Romans 6:23 "For the wages of sin is death, but the gift of God is eternal life through Jesus Christ our Lord."
"Death" refers to spiritual death; the separation of man from God for all eternity. But God gives us a gift: eternal life through Jesus Christ. He does not force it on us; we must choose to accept it. But once we accept it, it is ours. We do not have to pay for it or work for it; it belongs to us forever.
Romans 5:8 "But God demonstrates His love for us in this: While we were still sinners, Christ died for us."
It would be hard enough for one of us to die for a best friend; but while we hated God and did everything against Him, Christ still loved us enough to give His life for us. That is a love that exceeds anything we could imagine.
Romans 10:9-13: "That 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."
"For it is with your heart that you and are justified, and it is with your mouth that you confess and are saved"
"As the Scripture says 'Anyone who trusts in Him will never be put to shame'".
"For there is no difference between the Jew and Gentile - the same Lord is Lord of all and richly blesses all who call on Him."
"For whosoever shall call on the name of the Lord shall be saved".
That is what makes a Christian a Christian. There is nothing you can do yourself; the work has already been done. What you must do is accept it. The Lord wants you to come to Him; won't you do so today?
All verses are taken from the New International Version of the Bible.
Verses should all be read in context.