So, sort of an exercise in roleplay?  I can do that.

I think “how would other trainers treat them?” is sort of too broad a question – we can see in the games and especially in the anime that there are a lot of answers!  Think of Ash and A.J. in the Path to the Pokémon League, for example, and then compare both of them to Jessie and James.  Compare Alder and Giovanni – it’s night and day.  The real world would doubtless be even more complicated, because what we’ve seen of the Pokémon world is (or at least seems to be) quite culturally homogenous, which our world isn’t.  You could fill a book with that stuff.  I can talk about myself, though.

I see Pokémon training as being, in an ideal world, a sort of mutually beneficial contract.  The trainer has greater freedom to define the terms of the relationship – the Pokémon’s main options for renegotiating are to refuse orders in battle (which could end painfully) or to leave outright (which, depending on the circumstances, might be undesirable).  This makes it the trainer’s responsibility to seek approval from his or her Pokémon before making decisions that affect their relationship and ensure that they have the opportunity to leave on favourable terms, purely as a matter of courtesy.  For instance, I recently moved from New Zealand to Ohio – if I were bringing Pokémon with me, a big concern would be making sure that they understood what that entailed and had a chance to refuse.  Some things can be assumed – unless they’ve been fighting already that day, I think I can generally expect my Pokémon to be willing to battle.  Anything out of the ordinary should really be run by them first, though; if I’m leaving town for a few days, they should have the option to come with me or stay at home; battles with Gym Leaders should wait until they feel ready.  Pokémon can’t talk, but they’re pretty sharp by animal standards and seem to understand a good portion of whatever is said to them, so a big part of interaction should involve simply talking to them, learning to read their responses, and getting used to the way they communicate their desires.

My philosophy for training rests on two assumptions: first, that Pokémon work with human trainers because they desire wider experience than they would enjoy in the wild; second, that Pokémon intend, at least in principle, to return to the wild at some point.  The first of these, to me, seems axiomatic; the second may well turn out to be false, but I think the healthiest practice is to assume initially that it is true.  The way trainers develop their Pokémon’s skills should reflect this.  I would see my principle responsibility to be researching techniques and studying the capabilities of different species of Pokémon, and giving my own Pokémon the opportunity to try out many different attacks.  I also think that one of the most significant types of ‘wider experience’ trained Pokémon gain is working with Pokémon of different species, so I would place a priority on double battles.  Exposure to the human world is important too – look for opportunities to hire them out for things other than battling, like construction for big Fighting-types, or aerial survey for Flying Pokémon.  If I had the time and energy, I would prepare food for my own Pokémon, but this is more a matter of preference than any comment on training philosophy – I just like preparing food.  Most of any money won in battles or earned for performing tasks should go back to the Pokémon, in the form of food, toys, training equipment or medicine.  Pokéballs should be regarded as tools for specific purposes – they can offer protection, facilitate travel, and provide a place to sleep, but the majority of a Pokémon’s waking hours should be spent outside when circumstances permit.

As for Pokémon who don’t meet expectations, I think the most important thing there would be for the trainer to assume nothing – especially don’t assume that the Pokémon is in the wrong.  The first thing to try is to look for areas other than battle where the Pokémon might excel (this is one reason it’s good to spend time having your Pokémon working on miscellaneous projects) and figure out what skills it’s using there.  It could be the battle style you’re using just doesn’t match up with the abilities your Pokémon is most confident with, and you need to radically change its moveset to something that makes more sense for it.  Alternatively, battle just isn’t this Pokémon’s thing (in which case you should try to focus on other pursuits, like contests or non-competitive work), or maybe something just isn’t working in your personal interaction – either way, it might be a good idea to look into trading with someone you know to be a responsible trainer, ideally someone your Pokémon already knows.  In short – the point is to work with them, figure out (by trial and error if necessary!) what talents they have, and develop those talents in ways they wouldn’t have the opportunity to on their own.