Cracking the Nut

How do you all handle NPC actions in a "hotbed of political intrigue" interactions with the PC's? Do you heavily script the encounter, randomly roll, or rely on tables? How about the ever cascading complications from the PC's actions and gauging NPC's reactions? Specifically any behind the scenes info that the PC's would not be aware of? 

While in an average dungeon crawl monsters are prepared to act in rather well defined roles in the immediate tactical situation, providing a dynamic stage within the greater "world",and when to present antagonistic forces full on into the faces of the PC's  and make it a believable, logical  occurrence... I've always found a challenge. 

The old addage "if it makes for a better story, just do it" makes me feel good all over, it isn't the fine grain detail of some type of "method" I seem to be fumbling for.

Lately I rely on random tables for immediate, in game encounters than ruminate endlessly in between game dates on what to do with the situation.