Queensbury sits on the I-87 (the Adirondack Northway), about 200 miles north of New York City and 65 miles north of Albany. Driving is the easy answer: the I-87 is fast and runs the length of the eastern Adirondacks. From New York City, allow three and a half to four hours; from Boston, the same.
Albany International Airport is the nearest commercial airport, an hour south on the I-87, with direct flights to most major US hubs. Adirondack Trailways runs a daily intercity bus from New York City via Albany; Amtrak's Ethan Allen Express and Adirondack lines stop in Fort Edward-Glens Falls, about ten miles east, with bus or taxi onward to Queensbury.
Once here, you need a car. The local Greater Glens Falls Transit bus system covers some routes around the town and into Glens Falls but won't get you to most of the surrounding attractions.