Interesting factoid I learned recently: if you survey members of different scientific disciplines, you find the lowest rate of religious belief among psychologists. You might think it would be, say, physicists, who know in their bones that there's no logical room for a meaningful god, but apparently that doesn't stop them. OTOH, knowing in your bones that there are alternative explanations for religious impulses and having a framework to understand them -- while logically providing no evidence either way for the existence or non-existence of god -- seems pretty effective at producing non-belief in practice.

If I were trying to convert believers, I might try handing them a book on comparative religions in social contexts. "Here are 10 cultures, and how and why religion works the way it does for each"