Turn off the auger's engine immediately after it becomes stuck in the ground. You can try rocking the machine back and forth as well as side to side to dislodge it if a good portion of the auger is above ground. Do not apply a great deal of pressure since damage can occur if the auger blades are deep in the ground.
Disconnect the drive unit from the blade unit using the appropriate hand tools and set it to the side. Attach a pipe wrench to the blade or your model's optional proprietary T-handle.
Turn the pipe wrench attached to the auger blade counterclockwise to dislodge it. It may take several revolutions before you completely back out the auger blade from the hole.
Reattach the auger blade to the drive unit and start the engine. Continue drilling the hole steadily and slowly to avoid getting it stuck again.