What writing, specifically?
After sounding like a bloated ego with a keyboard for so long, I hope it's not ridiculous to discuss this from a point of no knowledge.
What writing examples are most valuable in a portfolio, or to have a working knowledge of before confidently calling yourself a narrative designer?
Script treatments? Dialogue? Extensive overview? Novel-form story?
It's not hard to assume that every one of these is something you should be working with, but in terms of getting noticed - what are your interviewers looking to judge you on? This implies the corollary question of what all narrative designers do, i.e. pure script (playwright-style), dialogue, setting, all of that nonsense, etc.
Also, for the non-pros, what skill sets are you guys all developing? There's a lot of discussion of, "I have talent and passion and whatnot, but nobody has hired me," so I'm curious as to what exactly that process has entailed for you all.
Signatures=pretense. And I'm far too well read for that. :D