Why write about GMing? You have to learn by experience and no plan survives contact with the enemy, right?
I'm with Clausewitz:
"Theory is instituted that each person in succession may not have to go through the same labour of clearing the ground and toiling through it, but may find the thing in order, and light admitted on it. It should educate the mind of the future leader in war, or rather guide him in his self-instruction, but not accompany him to the field of battle: just as a sensible tutor forms and enlightens the opening mind of a youth without, therefore, keeping him in leading strings all through his life.
"If maxims and rules result of themselves from the considerations which theory institutes, if the truth concretes itself in that form of crystal, then theory will not oppose this natural law of the mind; it will rather, if the arch ends in such a keystone, bring it prominently out; but it does this only in order to satisfy the philosophical law of reason, in order to show distinctly the point to which the lines all converge, not in order to form out of it an algebraical formula for the battle-field: for even these maxims and rules also are more to determine in the reflecting mind the leading outline of its habitual movements, than to serve as landmarks indicating to it the way in the act of execution."
-On War, Carl Von Clausewitz