2. Get rid of the Flash: A flash will be useless in large areas. Also, many famous houses of worship do not allow flash photography inside, so it's in your best interest to leave you flash at home. To compensate, use a faster film when photographing the interior, and if you have a portable tripod, definitely use it.
3.Try Different Vantage Points:** Just as you would move around outside when photographing the exterior, try a bunch of different vantage points when photographing the interior. Get low and use a wide-angle lens to exaggerate height. If there's a balcony you have access you, climb of there to get an aerial view, especially if there are stained class windows involved.
4. Remember your Manners.** You are at a house of worship, so be courteous and inquire about whether or not photography is allowed inside. Also, do not photography anyone worshipping, that way you can avoid being offensive.