Low impact, Leave No Trace camping is encouraged. Pedestrian is correct outlining the rules for the Catskills in particular. I once mistakenly camped too close to a trail one night and got a stern talking-to from a passing ranger the next morning so they do patrol the trails.
There are bears out there so hanging your food, toiletries, everything but yourself, etc. is recommended. Bear cannisters are not mandatory like in the Adirondacks. I have had porcupines scrounge around at night though, and one backpacker friend had to move out of the leanto and bivy outside after the resident mouse ran across his face for the 4th time.
You should also consider doing loops on the Devil's Path - steep climbs and tough trails but great views. Leantos and brooks can be found in the notches and there are numerous loops, although some road walking is always involved. It is something to build up to at least.
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