Five big tips for skeptics aiming at talking to believers.
First, know your own objective for the conversation, and make an effort to ascertain your interlocutor's.
Second, take stock of your interlocutor, particularly how intelligent and how emotional she is.
Third, stay civil. End it if things get something-other-than-civil.
Fourth, stay aware of, and make explicit if need be, the frame, structure, and rules of the exchange.
Fifth, be prepared for probable arguments and responses; and particularly with discussions of interest to skeptics talking with believers, there are ample resources available to help you with this.