In any debate, there's one party that bears the burden of proof. This means that it's their job to offer compelling reasons to accept their position, and it's the other person's job to stop them from doing so.
Traditionally, the burden of proof lies with the person making a positive claim. If you tell me that the moon is made of cheese, and I say that I'm unconvinced, then you're the one who's got to back up your position. I haven't made a positive claim, so I don't have to do anything.
As anyone who's studied any philosophy at all knows, you can't really prove anything. Is there a God? No idea. Am I just dreaming that the world's going to ruin? Could be. Do I exist? Haven't a clue.
This is why it's so important to avoid accepting the burden of proof in a debate. If nothing can be proven, then whoever accepts the burden of proof loses. It's as simple as that.
To shift the burden of proof onto your opponent, start off by asking them to explain why they believe what they believe. This sounds quite like quite a benign request, but as soon as they start to offer reasons for their position, they are taking a positive stance and so accepting the burden of proof. Once they do that, you've got them.