To fully know Jesus, and to know what Christianity is really about, involves active participation in community life and through developing relationships with other people, and not simply by learning propositional truths or facts about Christianity (even if we affirm there are propositional truths about Christianity). Christianity is not an idea - it's a way of life.
Jesus said "by this shall men know that you are my disciples, that you love one another" (John 13:35). He didn't say "the most convincing evidence of Christianity is fulfilled prophecy" or "people will know you are my disciples if you teach all the first principles simply yet thoroughly". What He said was, the only way to show people that you my disciples is to show them. We are called to live His teachings - to love one another.
Our best apologetic (and also our worst!), is our behaviour. Our behaviour towards each other can either attract people to the teachings of Jesus, or repel them. Bad behaviour can not only turn people away from the church, but also from the teachings which the church is supposed to put into practice. There are many people in the world who won't ever open a Bible because they look at Christians and don't like what they see.
I was interested to see that I was recently quoted in Anthony Buzzard's "Focus on the Kingdom" magazine (June 2006):
“Practical teaching without sound theology is as impoverished as sound theology without practical teaching. The New Testament doesn’t make the distinction between orthodoxy [correct doctrine] and orthopraxy [good practice] that we often do, nor is there any hint in the Scriptures, as far as I can see, that God will forgive bad behavior more readily than poor theology, or vice versa. We need to teach them both and teach them well.”