ePhotoZine has posted a brief piece on how to shoot ruins - abandoned buildings and obsolete facilities. Clearly, the author lives in the U.K. - speaking of shooting abbeys and the like.
(Click Here) to read the entry on ePhotoZine
In terms of equipment, the suggestion is to bring a wide angle lens, a longer zoom, a tripod (either full-size or tabletop), and a polarizer.
For technique, the author suggests walking the site carefully before jumping in to take pictures. Give context to the rubble piles that you find interesting, rather than just shooting closeups of them. Try shooting out through window openings, and down long corridors. Also, consider including signs as part of detail compositions.
If you're able, get a high perspective for overall shots of buildings, in order to reduce distortion caused by having to point the camera upward. Another way to achieve this is to shoot the building from further away, using a telephoto lens.
Finally, consider shooting a panorama, if the site warrants it.
Here are a couple of recent shots by my friend Rob Svirskas (flickr id: robsv), taken at an abandoned Bethlehem Steel factory.