Getting titles wrong is one of the quickest ways to lose your audience’s trust. They’ll think that you don’t know what you’re doing or you don’t care enough to get things right. In fact, religious titles are quite a challenge.
Some titles indicate an official position and endorsement from hierarchy; others people choose to bestow upon themselves. Some—rabbi or reverend—are familiar, but many—sheik (in Islam), metropolitan (in Eastern Catholic or Orthodox churches) or reader (in Christian Science)—might not be.
Ask people what their titles are and what kind of authority they represent. If someone uses a title you’re not familiar with, check it. More guidance on religious titles can be found in the ReligionStylebook on this site.