I want to start an informal group in college. What I want to do is start some close relationships, but I don't want to cause weaker brothers to stumble and I would prefer the company of unsaved because my purpose is to evangelize, not preach to the choir. I want to put up signs around my campus with my e-mail address for anyone interested in joining. I can only have at most five or six people.

My original plan was to bluntly put "No Christians Allowed" on the sign, but I feel like something more subtle is called for. Since the group requires an e-mail to join, I figured I could ask beforehand some questions. What sort of questions could I ask to obliquely find out if the person, at least in name only, is a Christian? Ask for favorite philosophers (see if I get Kant and Nietzche or Augustine and Lewis) and musicians (see if I get Metallica Swedish House Mafia or TobyMac and Amy Grant)?