Yeah, I think the broad definition of total non-interference with non-warp cultures and non-interference in internal affairs of separate cultures succinctly encapsulates the definition offered us by the cannon.
In reply to R. Star:
1) Don't remember Captive Pursuit off-hand, but thanks for giving me an excuse to re-watch a DS9 episode
2) Sticky issue there. Was Gabriel Bell ever Gabriel Bell? Probably so, because Sisko would have seen himself as Mr. Bell having studied him in the Academy. So maybe there.
3) Someone pointed out that Pale Moonlight, while certainly a deviation from Federation ethics, is not a violation of the Prime Directive.
4) Yeah I guess, accepting the role as Emissary while still remaining affiliated with Starfleet might count. But he is the Sisko. So we have to allow him this.