“That which can be asserted without evidence, can be dismissed without evidence.”Start by asking them this: "What is your evidence for believing in god?" They have no sensible answer for this question. Invariably, they will offer mush in response, usually in the form of a word salad.
That's when you lay the Hitchens quote on them. It's everything you need to respond to a religious idiot -- all in one sentence. Hitchens will never die. He will always be with us.