From the 10,000 word post:
"If we rely only upon the player's narrative, the momentum of the campaign will quickly diminish. It is not what the players know that creates a fast-paced, unexpected game - but what the player's do not know ... For a good game, it is necessary for the DM to create other narratives which take place simultaneously with the party's narrative. We can call these "NPC Narratives" ... side stories the players don't get to see, but which occur chronologically in tandem with the player's decisions and actions."
To explain this, on the main post I used an example from Star Wars, comparing the chronological actions of R2 and 3PO with those of Luke & Co. in the trash compactor. That things happen simultaneously to other people (NPCs) around the party is fairly obvious - but how do you construct these things so that they affect your campaign?
The answer can be found in the stock events I spoke of earlier. Your NPC's, too, will be chasing after opportunities, combating scarcity and accumulating wealth also. As a DM, you need only consider what motivations your NPC's have, and how that shapes the temporal setting and narrative of your campaign.
I've been talking about setting for months; by now the gentle reader should understand that a setting is more than dimensions on a map. A setting encompasses the purposes of the occupants of that map also. They are trying to improve their miserable lives, bring their produce to market, fight off unfriendlies and shape the ordinances and purposes of their collectives. They live and breathe too, and they don't want to die anymore than the party does. Every NPC has his or her small stream of narrative in your campaign; hundreds of NPCs together form rivers of narrative, and thousands or tens of thousands form great lakes or seas of narrative. If your party desires to pursue their own agendas, they must be shown that sometimes the river flows with the party, and sometimes the river flows against the party. It all depends upon which course the party chooses.
What I'm saying is that yes, there is a sandbox; and yes, the party IS free to choose what they will and won't do. But there are quite a lot of others right there in the sandbox with them - individuals whom you, the DM, control - and they are just as free to choose their will as the party, in terms of how you perceive 'freedom.' As a DM, you must stretch your imagination to make those people come alive, and to define for you and for your party how those people agree, or disagree, with the party's actions.
Not everyone in your world is good. Not everyone thinks slaughtering the residents of a town is a bad idea. Not everyone is opposed to a little bribery on the side. Not everyone hates the local lord. Not everyone thinks the prices at the market are too high. Not everyone thinks the local ruins should be explored, or the residents therein wiped out. Not everyone thinks the same. Some people have different ideas of what is right and wrong. It is up to you to have a candidate from each constituency meet the party and discuss how the party's actions are praiseworthy or contemptible. Sometimes a fight will break out. Sometimes the party will be convinced to change its mind. Sometimes people just won't disagree. But what you want is for the party to recognize that the friends and enemies they meet along the way aren't made of cardboard. They're REAL - in your mind, at least - and they have legitimate reasons for believing whatever it is that they believe. They have legitimate reasons for trying to stop the party from doing what they want.
Doesn't mean the party can't still kill them. But it needs to be conveyed that the party is killing more than merely stick-figures, or plot-devices, or exposition-throwers. The orcs aren't just growling targets. Red Dragons have agendas too. Everyone feels scarcity. Everyone appreciates the importance of having friends. Curiousity touches every heart. Battle is an act of desperation, either to defend against fear, or to achieve what cannot be gotten any other way.
Sit down and figure out what your NPCs want. Figure out how they'll go about getting it, from planting crops to raising armies to slipping over a garden wall for a bit of nookie. Now figure out how those actions affect the party, who happens to be in the same garden, or upon the same battlefield, or walking along a farm road. See where the narratives cross, where they smash together, and where they flow together.
Worry less about the programmed information your NPCs must tell the party to make them do A or B. Have your NPCs already in the process of doing A and B, and let the party decide if they want to go along, stop the whole process, or ignore it. When you stop seeing your NPCs as road signs and pamphlets, and start presenting them as creatures with purpose, your game will improve in ways you've never imagined.