There are various types of NYS land, Parks, the Forest Preserve, etc. A State Forest is the least restrictive, logging of the land is occasionally done. Charleston State Forest is a large and somewhat disjoint section south of Amsterdam. It has a variety of trails which you can ride, some singletrack and other double track or old roads. It is also popular for skiing in the winter and there is some horse riding there. A map of the forest is shown below.
The best section to start riding is probably between Hughes Rd and Burtonville Rd. I have marked a parking spot on each of these roads. After you do the trails there you can venture south of Burtonville Rd. On the trails that I have not taken gps readings I have written “No” or “No GPS.” These are trails that may or may not be there.
To get to the state forest, from the southeast side, like from Duanesville, go west on Route 20 and then take 30A north. From the north like from Amsterdam take Route 30 south just a few miles and skid right onto 161. Follow it to Schoharie Creek and immediately after crossing the creek turn left on Hughes Rd. Follow it to the parking area.
To download the Charleston State Forest map, right click the link and select “Save Target As…” The map is pretty complicated and you should probably print it on a sheet of paper larger than standard letter size.
Charleston trail map