Unless the transfer case has a neutral, there are only two ways to do it right. The first is like Still Pat did it, pulling the rear driveshaft. The second is pull it backwards, having the front wheels roll. Either way, must be in 2wd.
The transmission 'can' get wrecked when the driveshaft (and thus the transmission output shaft) is spinning and the engine (and thus the transmission fluid pump) is not spinning. Some of the internals are turning, but no fluid is being pumped to lubricate everything. That's what automotive theory says, anyway. I've seen transmissions wrecked within 20 miles of city-speed towing, and I've also seen them towed hundreds of miles with no problems. Maybe it depends on the specific transmission, I'm not sure. The transfer case will be okay because its fluid pump is turning any time its internals are moving.
As a side note, the first generation (60's?) of Chrysler automatics had the fluid pump in the tailshaft housing, meaning the pump was always turning when the driveshaft turned. Flat towing cars with this transmission would be okay. This design had the bonus of being able to push-start the car...yes with an automatic transmission!