One of the most common problems new explorers run into is how to find locations. Every regional board has at least one thread started by a new-to-UER person asking where the best local spots are hiding. The following is a compilation of tips and tricks that I use or have seen others use. Hopefully it will help point some people in the right direction.
This is just a general guide, and is by no means comprehensive. If others have tips and tricks that they would like to share, that is highly encouraged. I'll add to this when I come across new resources or think of things that I forgot to include.
1. Get outside and look around. This is the most obvious (and likely most used) way to find locations. The easiest way to find locations is by driving or walking around wherever you may be. Get outside and keep your eyes open! Scaffolding and fire escapes are good ways for getting to rooftops. Creeks in cities often go underground at some point, which will lead you to some sweet drains. Doors that are shut aren't necessarily locked.
2. Google is your friend. Google has helped me to find my favorite locations. Often just a few tidbits of information and 10 minutes of weeding through results will lead you in the right direction. Knowing the type of structure (theater, power plant, etc.) and a general location (city, town, etc.) is sometimes all you need. Occasionally you might need to dig a little deeper.
Google News search is a good way to find articles concerning construction of new drains, problems with old or abandoned buildings, complaints to the city about that terrible old factory down the road, new constructions that have run out of money, etc. The internet is a beautiful thing - use it!
3. Google Earth and Bing Aerial view and bird's eye view are great tools for finding locations. They can also help you decide if there are active buildings nearby so you'll know if you need to go during the day or pre-dawn it. Outfalls can be spotted this way too, although determining their height is often tricky. Sometimes the maps are outdated and buildings have been demolished, but this is a good starting point.
4. Flickr Searching "name of city + abandoned" will often lead you to glory. This can give you not only locations, but good information about security and maybe even possible entry locations. It will also let you know what shots are exhausted so that you don't come back with the same photos everyone has seen a million times. ;)
5. City resources/GIS Databases Some cities have put their GIS (Geographic Information Systems) data online. For example, Indianapolis:
http://imaps.indyg...lViewer/viewer.htm. If you zoom in far enough, you can look at the layer that contains sewer and storm drain maps. No size is listed, but using this in conjunction with Google Earth/Bing + walking around will definitely get you some good leads.
Not all cities put this sort of information online in such nice formats, but sometimes they will post about upcoming construction projects or have PDFs of such data available. Check your city of interest to see if such resources exist. Also, some cities (such as Detroit) are selling or auctioning off abandoned property. Checking their websites can lead you to locations sometimes.
6. http://Skyscrapercity.com (that's a link, click it!)
This is helpful for finding cranes and construction projects, if that sort of exploring is what you enjoy. It isn't always well updated, however. Sometimes construction sites will have webcams that track their progress. By looking through their past captures you can determine when workers are present and what security you might encounter.
7. http://Emporis.com (that's a link, click it!)
This is more of a historical fact finder website for explorers (although the site itself is real estate related). If you know a target building's name, you can enter it into the search and find out when the building was built, the architects, height, etc. This may be more useful after an explore, but I always find the history of buildings to be quite interesting.