My group does pretty much the same thing as omotm and hill pounder. As soon as I feel it starting to dig, I get off the throttle. Next I stomp a path in front of the machine and then stomp the snow right next to it. That way we lift the back of the sled onto the stomped snow, have someone pull the throttle and the other person pull on the ski and it comes right out. I found how not to get stuck:
1. don't stop going uphill. I always stop on a level (if you can find it) spot or facing downhill.
2. ride in groups if all possible. I never go into the back country without a cell phone and a partner.
3. have some idea of the terrain your getting into.
The rest you can forget, your going to get stuck. I did install a reverse Kit in my sled this summer. I got screwed up a lot last year trying to turn around in places I shouldn't have been. Where I live, there is nothing level (13 miles from Yosemite National Park). I went down a slope that turned out to be extremely steep. Thought my sled was doomed til spring, had to ride straight up out of a canyon between trees and stuff. that sled did it, it was hairy.