I don’t know. Scientific evidence that is reproducible would be a good start. The scientific method is the only method I’m aware of that we have to accurately explain and predict the natural processes surrounding us.
One thing I do know, if I were God and I wanted people to know I was real, I would know exactly how to do that. There wouldn’t be a question about which sect is correct, because I am all-knowing; I know exactly what it would take for each person.
But we also know that there are people who will not go to heaven, and instead will suffer for eternity in absence of God… So that means that there are people (quite a few) that God created knowing full well that they are “destined” to burn for eternity. Sorry, but that’s really fucked up.