I love urban exploration, the exploring of and photographing of abandoned sites.
Finding abandoned sites is the first obstacle. The best locations are rural towns that have folded under, either from industry moving out or mines closing. Most smaller towns have a periphery of industrial areas or farm areas that also possess a fair deal of abandoned sites.
There are so many safety tips that cannot be overlooked:
Carry mask filters. These places are filled with powdery debris and asbestos and it's best to be prepared. As fun as this passtime is, it's not worth leaving a site with permanent lung damage. Gloves, strong boots, flashlights and batteries, first aid kits, water, cell phone, and even a tazer or pepper spray are basics.
If a site has "no trespassing signs" some folks will ignore them. I do not. I will be arrested if found on the site. Without that posting and holding a camera, I can be forgiven and sent away. With some of the lenses on the market nowadays, there is not reason to go into a no trespassing site when you can film it from afar and legally.
Remember that indigents, troublemakers and wildlife could be inhabiting the building. Either make some serious noise or toss rocks at the building to get anyone/anything inside to come outside. It's always better to meet them outside than inside.
Pairing people up to watch out and photograph inside is a good plan. Two people outside seeing who might be approaching and two inside photographing and watching each other's safety, works well. Remember, floors and stairs and upstairs floors are all questionable. Do not assume everything is walk-able. For goodness sake, be sure your tetanus vaccine is up to date.
If you use the tab up above for Photos/Urbex, you will find lots of posts about urban exploration photography. My advice to you is to keep proportions in mind to enhance tall heights and make them every taller, or wide widths even more wide. Utilize lighting and darkness. Utilize plant life taking over and crackled and peeled textures. Use broken mirrors and glass windows to reflect things. Tell a story with a photo--not by showing an entire room or building, but only a part of it to represent the entire theme.
Enjoy the hobby of urban exploration and try and stop for a moment and just appreciate the history and life that once was held within those walls. At one time in its history, it was a refuge and a place of memories. If you look hard enough, you might just capture some of those memories.