When taking pictures of gravestones, always take at least one picture showing the relative positions of all stones you’ve photographed. The positioning may not hold clues, but it’s a good piece of information to get while you are in the cemetery. Pictures showing the relative position of the stones in the entire cemetery–or at least near landmarks within the cemetery–is a good idea as well.
With digital images, “wasting film” isn’t a concern. The best time to take the pictures is while you are right there at the source.