the most recent issue of Twilight Time had an article entitled Seven Deadly Sins of Character Motivation (part 1/2)

the basic idea is that NPC (or PC) motivation can be mnemonic'd using the seven deadly sins; in Sorcerer-speak this can translate into Kickers or, I suggest, links in relationship maps

(note: I understand the thinking behind blood-n-sex-only links, this is just a thought tossed into the fray)

of course, I'm a sucker for any kind of NPC shorthand (eg, the star sign personalities from Unknown Armies)

It looks like a neat article, and a very interesting site. I've bookmarked it so I can go through it in more depth later.

I don't personally have problems with PC-plot interaction. As a GM, I don't design a "plot" except for a broad premise until after I've seen the PCs and even then, I don't set up the fundamental "story" until after the PCs have interacted with each other and whatever vanilla I introduce or create on the spot as events warrent. I customize each and every plot to the PCs, and build up most of the backstory retroactively.

As a player, I try to be adaptable and "emotionally available" so that when the GM introduces NPCs and setting, I'm able to let my character aquire 'Stuff' (friends, lovers, enemies, property) based on opportunities presented.