The Bible's nowhere near as contradictory as many people claim. Besides, the Old Testament is pretty much worthless these days. Jesus himself basically said that anything he taught overrode the Law of Moses.
Actually, he said that he wasn't overriding the previous teaching, only completing it. He wasn't abolishing the old testament, as many modern christians like to think in order to disavow some apparent contradictions.
There are many arguments people can make for a god. Creation indicating a creator, as bunnerabb said is one. The old anecdote was that someone doesn't stumble upon a watch lying in the forest and think, "Wow, this watch came out of the ground." Instead they think the complexity of the watch indicates a craftsman, a creator. A good argument, but there are good arguments against it.
First cause is the strongest argument for a god in my opinion. Evolution says that everything comes from something. If you trace this back far enough, you'll encounter a first. Where did that first come from? The big bang? Where did that come from? A strong argument, but there are strong arguments against it.
But I'm not gonna give them. Pythagoras once said something like, "If there's no god and you believe in one, then you're no worse off than if you didn't. However, if there's a god and you believe in him, you're saved. If there's a god and you don't believe in him, you're screwed. So the thinking man should believe in god." I haven't taken this advice, but it has influenced me never to try to convince others there is no god. In fact it was one of the saddest days in my life when I stopped believing in god. But, alas, the world still spins...
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I ate a hooker half a bottle of knife.