As long as you remember that the CHARACTER cannot allocate Hero Points, as there is no such thing in the world, this question is fairly easy to answer.
> What would a pious character devoted to an occupational god
> (e.g. a warrior god, the canoe god, or Orlanth the Herder) do
> differently from any master of the occupation?
Spend time and effort (which translates into HP) on religious aspects of the occupational god. Non-religious masters will not spend points towards affinities, or YOUR_GOD_HERE Mythology (except for incipient God Learners), or Worship YOUR_GOD_HERE. If the character is spending too much effort on purely mundane abilities, his priests will start treating him as if he were just another member of his profession, and not as a devotee.
What the GOD thinks may be another matter, of course. In Cults of Terror, there is a mention of a Wind Lord who was notoriously UN-pious, but apparently kept the status, and even became a by-word for such behavior, not as a bad example but as an example of the freedom of behavior that Orlanth allowed.
In other words, the Narrator will have to make his own rule as to how much mundane occupational HP count towards the piety (ie, time/HP) requirements. A god with Piety as one of the quoted virtues will want more effort into religious matters than one who doesn't. And have the initial "correction" come in-game, not by telling the player that he needs to spend 5 more HP or he will lose his status (or even get one attacked by the spirits of retribution).
> In the case of the canoe cultist: He's been fanatical about canoeing
> at every opportunity and learning about the canoeing technologies of
> other cultures. For example, he spent much of last session scraping
> the bilges of a Maslo catamaran as part of an ongoing contest to
> befriend its crew and learn the secrets of the outrigger they have on
> deck. It's pretty clear that this kind of behavior is "pious", in the
> sense that it's just plain weird, and has relatively little to do
> with normal goals like greed, power, and glory.
No, these are social. This puts HP into a relationship with "heathens" who just happen to unwittingly use the tool of his god. If he spends time trying to teach them Mythology of His_Canoe_God, that might count towards pious actions, though. I.e., the equivalent of quoting pertinent scripture would work well enough to count as purely pious. OTOH, the Narrator should consider lowering the relationship with the heathens if the PC is too obnoxious (spends too many without spending any on mundane relationships) about it.
> However, it's not clear to me how a devoted worshipper of a god of
> warriors (e.g. Destor the Adventurer) would show his devotion in-game
> any differently from a mundane sword-swinger.
He is a devotee of a god of Adventuring, not a devotee of sword-swinging. Have him spend a certain percentage on Worship God, Mythology of God, or at least the god's affinities.
If the player doesn't mind the idea of the PC living in one of the Dead Places, you know that the player isn't doing it right.
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