Reddit mentions of Lake George, Great Sacandaga: Adirondack Park (National Geographic Trails Illustrated Map (743))

Check out /r/Adirondacks also.

I would invest in maps for the Adirondacks at the very least. National Geographic maps a decent 5 map set that covers the entire Adirondack Park. These maps show the locations of lean-tos. You can use them to select a destination and then plan your trip. If you visit any decent outdoor gear store in the city, they should have the maps for sale. You can also order the full 5 map pack online from Amazon. If you just want one map, then you probably want the map for the Lake George Region, which covers the Eastern Adirondacks.

I would strongly recommend investing in a guidebook also, as it will give you more information than just a map will- difficulty of certain trails, points of interest not to miss, etc. The Adirondack Mountain Club makes a decent one for the Eastern Adirondacks. You can purchase both the Map and Guidebook together as a package.

I'm not really sure what /u/SlateRaven is trying to say- there is no such thing as the "Adirondack Conservation Society" (I think they maybe mean the NYS Department of Environmental Conservation, which manages public lands in the park, or the Adirondack Park Agency, which oversees development across the entire park). There's also over 200 lean-tos located in backcountry areas spread across the park, so you've got a decent number of possible destinations to chose from.

Make sure you familiarize yourself with the regulations for backcountry camping- not doing this is a common beginner mistake, and you can be ticketed and fined for violating them. These regulations exist to protect backcountry resources and keep backcountry areas in as pristine and natural a state as possible.

A few important regulations:

• Campfires are banned in some areas of the Adirondacks, due to high levels of use and impact (there simply isn't enough dead and downed wood to sustain fires if every visitor has them). Make sure you double check if you can have one or not. Please be sure also to use only dead and downed wood (you can be charged with a misdemeanor for cutting live trees on state land, and they have too much moisture to burn very well anyways). Areas where campfires are banned include the Eastern High Peaks and the Essex Chain Primitive Area.
  
• Bear canisters are required for overnight food storage in the Eastern High Peaks, due to increased aggressive bear activity. If you plan to camp there, you'll need to purchase or rent one for use.
  
• Within 150 feet of any roads, trails, or water, you can camp only at lean-tos and designated sites. Designated sites are marked with a yellow plastic disc that says "Camp Here." This is primarily to protect water resources- shoreline ecosystems are particularly sensitive to camping impacts, and are essential for maintaining water quality. Just because a site looks like it has been used by others doesn't mean that it is a legal campsite.
  
• Tents are not permitted inside of, or adjacent to lean-tos. If tents are a priority (and they often are in summers in the Adirondacks due to the bugs) then you'd probably be better off planning to camp at a tent site than at a lean-to.
  
• Lean-tos are first-come, first serve, and must be shared with other groups until the lean-to is full. Definitely have a backup plan in mind in case the lean-to is already full when you arrive. And make sure to carry tents even if you don't plan to use them (not carrying tents because you plan to stay in a backcountry shelter is another common beginner mistake that can leave you caught out overnight without any shelter at all because the lean-to was already full).
  
  You can view a more complete list of regulations here: http://www.dec.ny.gov/outdoor/7872.html
  
  I would also strongly encourage you to familiarize yourself with the Leave No Trace Principles. There is a lot more to minimizing your impact in the backcountry than just carrying your garbage out with you.
  
  I hope this helps!