Urban exploration is the exploring of buildings and structures made for man, but long since abandoned. Some call it "UrbEx" for short.
Finding abandoned sites is not all that difficult, but heeding no trespassing signs and avoiding interaction with people of questionable industry (illegal aliens migrating and staying in temporary shelter, those who are in the drug trade, or perhaps on the run), is only part of the difficulty. As well, one has to consider safety in broken down and asbestos-laden environments.
Basic safety rules
2. Bring a first aid kit in your car.
3. Carry a charged cell phone.
4. Warn the critters and possible occupants you are coming by tossing some rocks at the side of the building to warn them, bringing them out instead of being cornered inside. I also carry a taser and pepper spray - just in case.
5. It's best to have a lookout who can look outward as you are busy photographing so you are forewarned if someone is approaching.
6. Heed "no trespassing" signs or you will be in trouble.
7. Listen and watch carefully for bee hives - they often happen in these old buildings and many africanized killer bees are now in colonies. Take care to learn what to do if you do get chased - the best option is to get into the car or a room where you can close the door and stop others from following. Don't just run - they can run for miles chasing you.
8. Google Earth the potential areas to learn a bit more about the lay of the land. You might want to pick an old abandoned mining town or small town and then look at the parameter areas of the region for the most abandoned sites and if Google Earth allows it, go to street view by dragging the "person" in the upper right corner of the screen to the roadway to see what it looks like from driving up.
LIGHT: I prefer to not use flash if I can help it. Most abandoned sites get some amazing light and it does some pretty cool things. If you use a flash, you essentially brighten the entire space and now it has no mystery.
Telling a story: You tell a story with your photographs by not showing everything. Instead of showing an entire room, show a corner, show part of a broken window and tattered curtain, making one wonder what the rest of the room is like.
Nature: Take advantage of what nature has done to an abandoned place.
Irony: You will often find misplaced items strewn outdoors, or perhaps an exit sign with a door missing or a safety sign with everything around it in devastation. Look for these things - they are priceless stories.
And, upon occasion, putting yourself in a setting can be quite interesting -
Here's my YouTube Channel Playlist for abandoned sites.