Stewart State Forest is a large area with easy singletrack. You could probably just rate all the trails easy intermediate and get away with it. The map below shows the trails. I have not yet ridden all the trails and have used a different color for those trails verified with gps and those not verified. There is not a lot of elevation relief here so I used 3 m (10 ft) contours. As usual the map is the UTM projection with the NAD83 datum, distance in meters. Set you gps unit the same and you will be able to see where you are lost at. You can see another map of this area at http://www.stewardsofstewart.org/.
There are several entrances to the forest, but if you are coming from the Albany area it is convenient to just use the Ridge Rd one on the north. Go down I87 to exit 17 and turn right on I84. Then get off at the next exit, highway 17K. Follow 17K west a couple of miles and turn left on Ridge Rd, which will deadend at the state forest just after it crosses I84.z If you see a bike shop on your right while driving on 17K you just missed Ridge Rd, turn around.
If you are new to this area what trails should you start on? My recommendations would include White Cloud, Camp, Windsor and Ants Line. Ants Line may not be the official name, I called it that after the famous climb at the Gunks. There are many large ant hill along the route. For easy trails I would suggest Orchard and Coaster. Again Coaster is not an official name, I used that because if you ride it north to south you just seem to coast around the turns. Much fun!
You can download this map as a pdf file from the link below. Since the area is large and the map detailed you may wish to print it on 11 x 17 or even 13 x 19 paper if your printer can manage the larger sizes. If you are printer challenged I have also supplied the map in two pieces, each of which can be printed on 8.5 x 11 paper.