Firstly: there have been 5 editions of D&D that I’ve played, and each has had a different take on Stealth.
Simple BECMI, AD&D, and AD&D second edition used surprise checks, thief skills, and (for the last one) nonweapon proficiencies like Camouflage.
These each worked differently and had different assumptions and effects.
The surprise check was rolled at the start of combat and modified for perceptive elves, who also had a 90% chance to take a for unawares (ditto hobbits).
The thief skill Hide in Shadows ditto, some percent chance to vanish, and ditto Move Silently.
Nobody knows how Camouflage worked.
D&D 3e and 4e used a more regular skill system, with various levels of specificity; every point invested in Hide or Stealth or Spot or Perception was a point not spent on Lute Playing or Ancient History.
It’s an odd grab-bag of things we’ve taken to bundling under this skill-umbrella: stealth, but not speed, spellcraft but not the spells themselves, diplomacy but not swordplay.
Bah, says I. 3e got skills wrong, and 4e doubled down on the error.
There’s a lot of interesting little rules-widgets mired in these so-called skill systems. I’ll talk about some others later, today I’m mourning stealth.
Pre-3e got this right.
Or, to put it another way, this isn’t a skill so much as a rules widget, a subsystem, a minigame.
It happens before combat as characters evade patrols. It happens in combat as Rogues go for the sneak attack. It happens in social situations as spies eavesdrop, and exploration as hobbits dodge nazgul. Monsters like to hide, pit traps are hidden.
Rules of thumb:
Reuse components. The last-ditch passive roll you make to avoid getting ganked is a saving throw — a perception save, let’s call it.
And you obviously do get a save, since getting caught by surprise is no good. By waiting to roll until the strike, you maximize the drama: yay.
Like attack rolls, have the active participant roll. That’s the sneaker usually, in movies. Ignoring that last-ditch save-yourself thing, anyway, it is: so they make saving throws against revealing themselves (at dramatic “they might reveal themselves” moments). These are kind of all-or-nothing, which means you needn’t track complex webs of who is aware of whom: fail a save, you made a noise/scent/sight. Detectors detect this with some radius based on wisdom, etc, and know there’s something somewhere even if not sure what.
This can also be the party rogue, rolling to avoid alerting the monsters…
When the active participant is the seeker, they should be rewarded. The math should be such that spending a round looking is a good thing that gives you something to go on, not a waste of time.
Finally, failing a search roll should only allow reroll in vastly changed circu
mstances: adding additional heads or time should allow success against some super-linear formula. Double the searchers or the time, add 2 to the total result. Something like that.