This is a hard rule to articulate, but one of the most important things I've learned as a father and teacher. I usually call it the Sideways Rule and it has many corollaries.
The essence of this rule can be grasped in the old story of two people arguing in a tug of war. You can fuss and fight and struggle, but nothing drops the tension faster than letting go of the rope. Direct confrontation tends to heighten the conflict and can even impair a positive message.
If you get into a yes/no struggle with a child (or adult) it quickly turns into a battle of wills, such that the subject itself can fall to the side. Instead of a thoughtful approach to the best decision, you now have something entirely different on your hands, which is the enforcement of will. If you watch children (and adults too), you can observe this constantly. What does a three-year-old want? Whatever the four-year-old has. And what does he want once he gets it? Whatever the four-year-old has now.
You can observe this in certain martial arts too, especially Tai Chi, where one's primary effort is in sidestepping and redirecting the opponent's energy, sometimes even using it against him. The idea here is to stay calm and poised, and to conserve your energy while your opponent tires.
But there is much more to this rule than conflict management. There are plenty of “positive” applications too. Tell a child to do something, and there's a good chance she’ll resist it. Start doing it yourself, and she often wants to join in.
Silke once said to me, "The goal of a kindergarten teacher is to be actively engaged in meaningful work, and then allow the kids to come and go, and play, as they please." Silke rarely gives explicit instruction to the kids. She is simply doing and being a living classroom and the kids can't help following her.
I’m narrowing in on the rule, but perhaps part of the reason it's hard to explain is that, like the rule itself states, we can't approach it head on.
Consider storytelling. I've approached children dozens of times with an “important lesson" simply to have it blow up in my face. Most children, at least at the 4-6 age range I'm working with, are not ready for so much direct communication. They need to be told a story (even if it’s a true one), or to have the lesson couched in a joke, a song, a doll or puppet.
Adults are like this too. Walk up to a friend or coworker and tell them directly to their face what they did wrong, or how they could be doing better. Who likes that? Why would a child like that? Try approaching them from the side, with a lightness in your tone, and recount a story or a time when the "wrong" thing is merely a peripheral element to the story. Chances are s/he will recognize their mistake and seek to repair it. What's more, they will be grateful that you graciously gave them room to recognize the error themselves instead of shoving it in their face.
Try it with compliments too. Sure, it's nice to say that someone is beautiful, smart or funny, but recount a story where their beauty or brilliance is simply taken for granted and they will probably shine even brighter.
Consider a child with a hurt finger or cut. Focus, focus, focus on the cut, the blood and the pain and you probably have a bad situation on your hands, even if it's a minor scrape. Whereas, if you approach calmly and address the ouchie without ripping apart the context or game at hand more often than not the child recognizes that the cut or bruise isn't so bad after all, gets up and keeps playing.
That’s not to suggest being callous or insensitive. Deal with life. Look at it head on. Sometimes things are serious. But whenever possible, approach from the periphery. There will be times when one has to shout and direct - Don't run into the road! - but whenever possible, start gently from the side. You will derive much more strength if the children follow you because they want to, and not because you demand it.
There is a great quote from Lao Tzu - "The greatest leaders are those we hardly know exist." The same could be said for teachers, and in a weird, subtle way parents too. In essence, if you shove every lesson down your child's throat, they will come to resent you even when you're right. But if instead you create an environment where the child has the sense that they discovered the rule for themselves then they feel confident, wise and proud. That is the goal.