Skeptic Daniel Florien asks his mainly atheist/agnostic readers what it would take for them to believe.
The first 3 of 87 responses (and counting) are:
"Evidence and an explanation that makes sense"
"Show himself and fix the world"
One commenter I've interacted with before said this:
"For me, god would have to demonstrate how the universe makes more sense with him in it. Something no religious person has ever been able to do."
I like how that first sentence begins. I groan when I get to the words "in it".