Depends on what kind of bottle hunting you are looking for and the geography of your area. I personally enjoy snorkeling in rivers and looking for dumps on the riverbanks. Water does a lot of the digging and work for you and new stuff gets washed out over time(if it's muddy you can get a potato rake and drag it along the river bed). If you want to find river dumps look at old maps of your county on google of old homesteads in your area, old bridges, railroad crossings, etc that are close to the river. Take a small kayak and explore, look at the banks for any old bricks or signs of broken glass(bring a fishing pole too might come across a huge pike!!!) Some of the small towns in my area are bordered by rivers that have old town dumps, other dumps I have found have been out in the country and are old 1890s to 1950s farm dumps. There is a website online that I believe will show the property lines and the homestead that owns the property.
Explore plat maps with powerful and easy to use land mapping and analysis tools. Find property lines, land ownership information, analyze soil quality, and more.
www.google.com
Finding a privy and getting permission I think can be more challenging. I do not have any sites I have found yet, but others on this site who have dug privys can help us both with that subject.