How would you know?

[Undeceived]

I'm an isolated islander.

How then, will I find out about god. More to the point, how will I find out about the christian, biblical god. And what happens if I don't.

Would you have God prevent people from being born on isolated islands?

On a soberer note, let's take a look at a few relevant verses:
Romans 1:20 "For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse."
Romans 9:16 "It does not, therefore, depend on human desire or effort, but on God’s mercy."
Romans 10:14-18 "How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them? And how can anyone preach unless they are sent? As it is written: “How beautiful are the feet of those who bring good news!”
But not all the Israelites accepted the good news. For Isaiah says, “Lord, who has believed our message?” Consequently, faith comes from hearing the message, and the message is heard through the word about Christ. But I ask: Did they not hear? Of course they did:
“Their voice has gone out into all the earth,
their words to the ends of the world.”
So there are a couple guesses: (1) that God's grace is self-evident to humankind; (2) that the person on the island goes to hell. After all, they do not deserve heaven, nor do they deserve a 'fair' crack at it. We, the disobedient creation, are at the mercy of God's grace; (3) the condition of your heart when you stand before the gates--i.e. what you choose then. All will confess, as Isaiah 45:23 says, “‘As surely as I live,’ says the Lord, ‘every knee will bow before me; every tongue will acknowledge God.’” Those who confess because they want the reward of eternity in paradise will go to hell (they want heaven without God). Christians will be those who desire to be with Christ, rewards set aside.
In answer to what believers did before Christ, see Romans 4:3: “Abraham believed God, and it was counted to him as righteousness.” This is the same way Christians are saved in the New Testament. Have faith and God will forgive you. Since God transcends time, it doesn’t matter when Jesus made his atoning sacrifice, as long as he did. This ties in with option (1), that people can find God in his creation and subsequently put their trust in him.