Christina Dickson in this post covers a number of tricks one should adhere to when photographing churches.
The first and third and somewhat related. Just remember that churches are a place of worship. I would add that you should ensure that the church grants you permission to take pictures. Most, but not all do.
The fourth and fifth are my favorites. My best shots are those where the light penetrates the church or when I was able to find a striking angle, especially using my Sigma 8-16.