Working on understanding .d/.tra files now - so a .d is like a script, and a .tra are the character's actual lines. Got it.
I like the flexibility of the .d format. Okay, so I can set up variable responses. One for an evil dwarf, the other for a goody-goody pally. Cool.
As Wes has said, the best way to write .d is to read .d. and read the IE file format hacking project.

Possible character concept:
Lawful evil (think the monk henchman from NWN if you've played that) human monk named Lao. He's a nihilist. Romancable by female PCs (that will come later).
Any ideas for "cool monk NPC things"? I'll probably stick with my existing char concept.