For me, it's entirely circumstantial.
If it's a situation where I feel the minions would look different--either in terms of physical appearance, equipment quality, or what have you--then I'll mention that in the description.
But if it's a situation where I don't think there would be a visible different (if there's no good reason for the minions' equipment to be sub-par, for instance), then no, I don't tell them, and they get to find out in combat.
In no case would I use the terms "minion" or "elite" while giving descriptions.
I was curious, so I checked--out of all of the skills with monster knowledge components, none of them are for Humanoids. I would have to house-rule some other skill in, I suppose. Dungeoneering for goblins and kobolds, maybe orcs. Nature possibly for elves or eladrin--even though they're just close to nature, not directly a part of it. And perhaps it doesn't have to be restricted to monster species type. Streetwise could give monster knowledge for bandit types, while History could help with military style units.

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