Also, by following their arguments, trying to clarify it and understanding the pieces. Your sincere and genuine attempt to understand them in the best possible light will make them open to your point of view.

The smart Christians are some of the most logical people I've ever met. There worldview fits together like a kind of Geometry. They know that you get a completely different form of it if you substitute one axiom for another (existence of God for non-existence of God), much like Euclid's world dissolves without the parallel postulate.

Once we got to that point in our conversation, I realized that they we agreed on everything about the world except that postulate, which they were also aware of. I realized that they were neither stupid nor evil, as I had assumed before (a remarkably common, and uncivil, view that atheists have of believers). I still disagree with them. However, I was fine with leaving the conversation with both of our positions unchanged, but understanding each other better.