Ground Rules for Debating God's Existence

Earlier this month, the noted agnostic Oxford philosopher Anthony Kenny died. He was considered to be fair-minded in his assessments to both the theistic and the atheistic sides of the debate. He readily acknowledged that the idea of God was the most significant one in all of history:
“If there is no God, then God is incalculably the greatest single creation of the human imagination. No other creation of the imagination has been so fertile of ideas, so great an inspiration to philosophy, to literature, to painting, sculpture, architecture, and drama. Set beside the idea of God, the most original inventions of mathematicians and the most unforgettable characters in drama are minor products of the imagination: Hamlet and the square root of minus one [i.e., an imaginary number] pale into insignificance by comparison” (Anthony Kenny, Faith and Philosophy [New York: Columbia University Press, 1983], 59).
In our Socrates Cafe over the years, we have had some conversations about the existence of a personal Creator God. Some attendees have dismissed God as a psychological projection, an unfalsifiable delusion, an anti-scientific idea, a superstition. Others have defended God's existence as credible, rationally believable, and as making excellent sense of the world and our human experience.
Here is the topic we want to discuss: if the atheist, agnostic, and theist are to engage in principled debate, what are some important ground rules to follow? Often, the opposing sides of the conversation are dismissive of any proposed argument from the other side. But how should we engage one another?
This conversation is not so much about defending one side or the other, but rather about how should *both* sides engage with one another. We want to discuss what are some helpful ground rules that can help guide the discussion?

It will be good to meet in person after a summer of just having online discussions. See you all soon!