My house rule is to allow an end of dpell save to see if you realize you were charmed. But you may have advsntsge or disadvantage depending on if the things done were against charscter trsits, with character traits or neutral.One houserule I've added to the various charm spells is that you don't automatically know that you were charmed when the spell ends. You make an Int/Arcana check against DC 10+spell level to determine if you realize it. If you fail, you internally justify your actions, and will still be somewhat friendly towards the caster.
I agree, that is where " practically" comes into play.If you got dedicated roleplayers at your table and you secretly tell one of them that his char is dominated by a mob e.g. a succubus without the other pc noticing, then you can have super fun. All the other chars desperately trying to figure out why the charmed char behaves so strange suddenly.
Did this once at my table and it was perfect. I even gave him saving throws from time to time, but the DC (18) was quite high. I did not have to intervene once because he was roleplaying the situation so good.
Probably the easiest way to "mind control" adventurers is to just offer them gold and XP to go do a thing the NPC wants.
Actually, in one of my 3.5 campaigns, the PCs had been marching and Stomping their way up the food chain of a villainous organization and as they approached the city the mastermind was centered in...I dont use xp, and all players level up at the same time. Unequal xp is not a playstyle I care for.
But yeah, something like that, some kind of reward for roleplaying the Charm well.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.