I only do religion if it has some effect on the plot in some way. Otherwise, I don't mention it. I might put it in the character sketches, but I don't use it in the main story.
I do have pieces and a novel that have good bits of religion in them, but those are connected with the other essential elements in the story.
Now, if a character teaches Sunday school or is a minister, nun, priest, rabbi, monk, or imam or the character sees first and meets his beloved in a church function or is suppressed or elevated by religion, then religion is open market to me. Otherwise, I skip it.