One concept I've run into in some stories and some testimonials, is of someone being moved to pray for some group of people, or person. That person is having a significant trial or in danger.
It reminds me of David Marcoe and his Calling of the Light miracle where he destroyed a lot of vampires. It may have been mentioned then as well. But you could easily have seen several dozen people moved to pray for something which would have assisted Marcoe.
The other way is of course for the faithful verser to be moved to do something, wake up in the middle of the night and pray, or something.
The way I'd run this as a rule is a GE roll that leads to a sit-mod bonus. Of course, this only applies in universes that have a substantial number of correligionists who have the view needed to do this, and the capability to do so. (Some faiths might not emphasize such, and even those that do, you have cultures in that faith that don't lean that way.)