Lighting is one of the most effective ways to put across the mood of being in an abandoned site. Nature has a way of pushing light through every single crack, hole, broken window, and missing roof. Utilize it to show the nature of dark corners and encroaching outdoors.
This shot (above) was taken in an abandoned prison where someone had scratched Nazi hate on the wall. The bars of the cell (not using a flash) created a shadow on the wall I captured and that happened to obliterate the awful writing. Poignant moments like that need to be noted and utilized. Had I used a flash, this would never have happened, but in studying the site before photographing, I noticed the artistry of it. Give yourself the time to study it and if you are utilizing light, do not use the flash or you will lose the beauty and contrast.
Capturing the light hitting something in the room and making it the focus can be quite poignant.
Use windows to reflect what's behind the photographer and show the whole 360 scene.
Or, use windows and doors to frame the contrasting beauty outside with the neglected interior -
(above) more effective at a tilt to show the funhouse effect of this narrow abandoned prison.
My best advice is to study the building and how the nature light is coming in. Turn the flash off on the camera. Have at it from every angle!