It's hard when it comes to the english side of things since both Wizards and TPCi are pretty terrible at cataloging or classifying cards. There are a lot more cards out there that I'd consider 'variant' before promo any day. I know I wouldn't poke that mess with a six foot pole, that's for sure. I will say regarding POP cards: the POP series cards I'd consider promotional. They may come in boosters, but if you were being pedantic they'd be a substitution set. Substitution sets are not part of the main release block, thus are promotional in my books.
When it comes to the Japanese ones, it's so much easier. Promos fall under a year category instead of one huge "Whoever-Runs-TCG-Now Black Star" list. 1996~7, 1998, 1999, 2000 etc. For the "un-numbered" promos from 1996 through to 2000, there is an official listed ordering for them, and that's by time of release during that year. Afterwards, it was a numerical system (P, ADV-P, PCG-P, DP-P, DPt-P, L-P and now BW-P) which doesn't always flow exactly to a number order due to releases being varied, but otherwise keeps things orderly and very distinct in what is a promo or not.
Decks are considered promotional, as they're essentially substitution sets and 99% of the time are
original cards exclusive to those decks or kits. Substitution sets are not part of the main block, and get shoved under the deck roster in the official catalogues and are thus: promo. Rumble set? Promo. Southern Islands/Tropical Islands? Promo. BW Beginning Set? Promo. And so on.
PCL certainly made things easier on a pedantic order freak, that's for sure.