My sister would say that in order to be a true Christian, you would a) have to believe that God exists; b) that Jesus Christ is His Son, and c) that Jesus is your Savior/He died to pay the penalty for all of your sins. However, in my view, it all depends on how you define the word "Christian".
It seems to be true, though, at least in American culture, that if you call yourself a Christian, you believe more along my sister's line of thinking than mine (meaning that someone who follows the non-theistic teachings of Jesus can call themselves Christian). Who is right? I don't honestly know.
Question: Is it better to believe so staunchly and fervently in something that (in your mind) you are 100% certain you're right, OR is it better to allow for the possibility that you might be wrong, and admit it? By "better", I mean "better for humanity", whatever that means. Mumble-mumble-mumble!