I know I used to practice that destructive ideology, by telling anyone naming Christ, that they are not a Christian at all, if they were not living by my pentecostal holiness standard...We used to make more enemies out of 'compromised' Christians, the the sinners not naming Christ at all...
Now we are getting quite deep. Paul in his epistles (and forgive me but I don't know which letter or verse and haven't the desire to chase it down right now) says to encourage those of weak faith, strengthen and not further weaken them. He was speaking about diet and circumcision but it applies to all other areas in life. At this point I think we need to remember this since these words will live online forever and we don't want someone who is "just feeling the waters" to get spooked.
Honestly, the best teaching is sometimes silence. Sit and be with someone and let them know the strength of your faith without words. Let them witness your faith in action. Let them see how you live and treat others and how you love and respect God. Then -- only then -- tell them about Jesus and salvation. So many get the order wrong. They start with the hook and all people feel is getting poked and feeling the pressure to conform and be something they are not. In the end it scares them away. An we, as Christians, will be called to answer for that when we meet God, and that's not a conversation I look forward to.
So I avoid the names, and the jargon, and the Bible-speak and I lay it out as simply as possible. Look to Jesus. Believe in him. You don't need to understand how it works -- you can't! Even if you lived a thousand years and had an IQ of 250 it still would be a mystery. Just accept this is so and let the rest go. Don't worry about anything else. If it's going to make sense then in time it will, but if it never makes sense that's OK too.
Now that we have the hard part done, look at how your life will change -- not all at once but in slow measure, perhaps faster in time. You'll find yourself being a little nicer, a little kinder, as you see others struggling through life. You'll see some have more light, and others a bit darker, and you'll see a pattern and want to change. That's the Holy Spirit at work. Again, don't ask how it works. Just accept it does.
One day at a time, one person at a time, one choice at a time, let it seep into you. Suddenly you look back and are amazed at how far you've gone. Sure, you'll be tempted and you'll probably even give in. Sometimes it will feel like God has abandoned you but he hasn't. He's just letting you understand. Then you pick yourself up and take another step.
That's what being "Christian" means. Everything else is a distraction.