"I'm talking about general principles or rules of thumbs with which to understand how to break down kata, or how to apply kata movement to technical application."

There is some very useful ground covered regarding kata application by Iain Abernethy on his website, and by the book below.

"The Way of Kata: A Comprehensive Guide for Deciphering Martial Applications"

Just a few are:

Each technique should be able to stop the attack.

Each technique should be virtually fail-safe (not dependent on "fine" motor skills in high stress situations).

The techniques should NOT require a specific response to work (I do this. Now he does this and viola!).

Our chambered hands usually have some opponent's parts in them.