From a Biblical perspective, the marks of a Christian are: 1) They trust in Jesus. John 3:36; Galatians 2:15-16 2) They have the Holy Spirit. How can you tell if someone has the Holy Spirit? By their attitude to Jesus. Is Jesus their Lord? 1 Corinthians 12:3; Romans 8:9 3) If the above are true of a person, then this third point must be true: They have a changed life. e.g 1 John 4:7. (Of course until Christ returns, Christians aren't perfect). 1 John may be very relevant to your question. How does a sinner enter into a relationship with God? By trust alone in Christ alone. Galatians 2:15-16; John 3:36; Romans 3:21-26). This part of the Christian message is very clear in the Bible and can't be compromised on. In the issue of day to day experience with Christ, for me there are many things I could say, but I'll just say four: 1) Every day I have to consciously choose to put my trust in Jesus and submit to His rule. Every day is a day of repentance and faith in Jesus. 2) It is of utmost importance that I keep focused on the death of Jesus. Why? There are many times I will sin/rebel/fail to trust in Jesus and treat Him as Lord. This and other factors, is why it is so important for me to keep focused on Christ's death for me. Because it is there I see and am reminded that God loves me (Romans 5:8-11) and it is there I see that He has dealt fully with my rebellion to restore my relationship with God (Romans 3:21-26). So when I fail, I look there, am reminded that God has paid the price for my sins, ask God for forgiveness and trust that because Jesus died for me, I have God's full forgiveness. I move on, determined to keep trusting in Him. 3) The gospel (message about Jesus) is not only used by God to make Christians, but is also used by Him to keep Christians growing and persevering in the faith. 4) Being a Christian is like a marathon, not a short sprint. What is more important than how one becomes a Christian is how will they finish. Will they keep trusting in Christ till the end? So I leave you with a quote from Hebrews 12:1-3: "Therefore, since we are surrounded by so great a cloud of witnesses, let us also lay aside every weight and sin which clings so closely, and let us run with endurance the race that is set before us, looking to Jesus, the founder and perfecter of our faith, who for the joy that was set before him endured the cross, despising the shame, and is seated at the right hand of the throne of God. [For] consider him who endured from sinners such hostility against himself, so that you may not grow weary or fainthearted" (ESV).