IMHO, I'd start with building a shelter. If you're going to spend some unexpected time outside, you'll need shelter from the elements, be it cold, heat, rain, etc.
Second, I'd go for firestarting, something that isn't as easy as some think it is. If it's cold, you'll need the heat and peace of mind a fire can give. Just do it safely, we don't need to start a forest fire to keep warm.
Third - probably communication. Good communication, be it a cell phone, a personal radio or even a PLB may turn a cold night and long walk into a minor inconvenience.
Fourth - probably signaling or making yourself visible.
Fifth - can you teach common sense? Using your head and not getting into trouble in the first place.