Metagaming is one of my favorite topics for getting to know other DMs, because I think there's an enormous possible range of views about it! Some scenarios that might be interpreted as metagaming:
- PCs encounter a Troll. They've never dealt with Trolls before, and maybe you gave them a Nature check and they didn't do well enough to know that Trolls have Regeneration which can be thwarted by Fire or Acid damage. The party Wizard casts Fireball on the Troll. Was that metagaming, since maybe the player knew he should pull out a Fire spell? Or is it fair game, because either you're okay with the player's accessing their own mastery of fantasy genre lore, or maybe that Wizard always uses Fireball anyway! Although it MIGHT be metagaming (depending on whether this was an unusual choice for the Wizard), there's not really a graceful way for a DM to deny the spell. If you know your players have certain knowledge mastery outside of their character choices, one option is to alter your world to surprise them! Maybe in this world, Trolls are instead thwarted by Cold damage.
- One PC (A) has a secret that the other PCs don't know about, but the players at the table are aware of (or at least know there is a secret, if not what the content of the secret is). In the night while the others are sleeping, PC-A does some sneaking around related to their secret, and as a result doesn't sleep very much. In the morning, one of the unknown PCs (B) asks around the morning campfire "So, how did everyone sleep last night?" thereby possibly requiring a Deception (or Bluff, etc) check from PC-A if they want to conceal their midnight activities. My opinion is that this wouldn't be metagaming--even if PC-B doesn't ALWAYS ask this question in the morning, I think it's fair game.. but I have encountered other DMs who say they wouldn't be okay with it. Now if a third PC, PC-C, takes a step like... snooping through PC-A's things to look for something secret, that is where I might draw a line. First, I would consider that PvP, which is not allowed at my table except consensually, but I would also probably question the line of activity and steer the player to make a more appropriate character choice. I can see how some DMs would be more protective of PC-A's secret, though, especially if the players have shown tension about this previously.
- The party hears about a local threat and decides to investigate. Even though the townspeople don't have any information other than "It's incredibly dangerous," the party decides out of game to go without hesitation because "The DM wouldn't kill us. They know our level and have probably scaled any encounters to be appropriate for us." Which... I'm fine with those assumptions. I can still surprise them if I want! But I can understand some DMs finding it inappropriate, because it's not very good roleplay for how the characters likely experience this scary information.
Although these are pretty different types of metagaming, they all have one thing in common, which is secret information: information about a Threat/Encounter or about a Story element. So then I just ask myself what is important about the secret--what did I envision being better about an encounter if they didn't know the Troll's weakness? Maybe I was hoping for a cool moment of discovery that happened when they used the right tricks during battle, but there's no guarantee of that.
Often the point of game secrets isn't to keep them secret forever. So what are we hoping to get out of revealing them, and how will the enjoyment/story/drama be altered if the reveal doesn't go as planned? That's what I ask myself any time I want to withhold knowledge from my players.
When it comes to knowledge that a
character should have but that the player doesn't have... I'm not actually sure what the name is for that, but in my experience this problem solves itself pretty easily! If it's something like an actual puzzle that the high-INT Wizard would probably be able to solve, I still like to give all the players a chance to solve it themselves, and if that fails, then I let the Wizard roll for INT. If it's knowledge about the world or an area of expertise, I just briefly discuss with the players. Some examples:
"Would I know anything about how to approach the Lord? He's heavily guarded..." "Yeah.. because of your Noble background, you know the protocols. You should find his footman. Roll Investigation."
"Oh, I didn't know there was a god of thieves! I shouldn't have said that thing I just said..." "No problem, you'd have known about that god, pretty much everyone in this world knows about him. We can retcon.. what would you have said now that we've established you're familiar with this?"
