Developing self-discipline in others is simple, but not easy. Personally I think that telling someone to lead by example is pointless. You lead by example whether your example is good or bad. Some cadet officers and sergeants think that they have the right to live like pigs while they require their subordinates to keep their personal areas inspection-ready. I've seen cadet officers eat McDonalds in front of airmen who had to eat cold pancakes and sticky oatmeal.
Nothing breaks down discipline faster than unfairness and arrogance.
As I said above, creating a disciplined unit is simple, but not easy. It requires the cadet leaders to act in an impeccable manner. It means the cadet leader is the last to go to sleep, the last to get out of the rain, the last to eat, and the first to get up in the morning. That cadet is certainly not going to make the effort to stay disciplined for a leader or organization that doesn't care about him or her. A good rule of thumb is that the only privilege of command is command itself.