I'd agree with everything mentioned thus far. Some of these things are pet peeves of mine, some not as bad. I'll address them, as well as work-arounds I use.
A) Monster lore that your character has yet to encounter, but YOU as a player have faced numerous other times with other characters
This is a big pet peeve of mine, and one that takes a lot of the excitement out of the game. On the other hand, it's not all that fun for a player who's faced a particular monster before (say a flesh golem) to purposely cast spells at the monster that he (as a player) knows will have no effect. It's sometimes hard to draw that line between player and character knowledge...
"Hmmm...I know that my lightning bolt spell, which I really do like using against tough opponents, is going to actually heal the flesh golem, and so do the other players, but my character will probably want to use it anyway, right?". It's almost like you're playing against your own character. My solution? Several things:
1. Throw new monsters at the players
2. Use variants of existing monsters with new powers or different vulnerabilities
3. Use unusual work-arounds. Are the players actually going to automatically notice that
ring of fire protection on the finger of the flesh golem?
4. Use the normal monsters in creative new ways. Maybe that flesh golem rolls around in mud or clay to coat itself, thus protecting itself against fire, things like that.
B) Lore on an adventure you've played in the past, but is new to THIS character
This is why I rarely ever run the same adventure for the same group of players. So it really isn't an issue for me. If I do run the "same" adventure for a group of players, it's "the same" only in the sense of perhaps they went through much of Level 1 of Undermountain, now they're going back. Same place, same layout, but enough changes to where it doesn't make a difference and in fact may work against the PCs if they (think) they already know what's there. I think that's the only solution. You really can't run the same players through the same adventure twice and make it fun or challenging without making massive changes to it.
C) knowing what spell/magic item X does, when you've just found it, but your character is not a spell caster
I've never had much problem with this, mainly because I like to create new magic items, or variants, or I give out items that are standard in the DMG but I don't tell the players what it is. This one usually isn't an issue for me.
D) knowing what is going on to friend ABC, when they are not there (IE your thief is out scouting 300 meters ahead in the dungeon. You can't see/hear him, when he gets in trouble, but you still go to his aid.. Just because)..
Yeah, this is a pet peeve but again one that doesn't really come up much. If it does, I simply inform the players:
"Your character could not possibly know that, so what are you actually going to do?". Or I'll simply say
"Ummm...metagaming?" and they get the hint. Doesn't usually cause problems. The response is usually:
"Yeah, you're right, I get it. OK, so I do this instead." Problem solved.
E) instantly trusting a new character who shows up to the group, just because he's a replacement character for a player who either had to make a new one, OR because he's the character of a new player..
This one bugs me, and I've seen both sides of the coin just like JadedDM mentioned - sometimes they simply don't trust the new character at all, to the point of paranoia. I've found that usually if there's some sort of in-game background to the new character, that makes things easier. For example, if a player has his character die permanently and he decides to simply start using a former NPC that already exists and has encountered the PCs before, well...the PCs have already dealt with him so they know he can be trusted and why. Or that he can't be totally trusted and why not. Or that he can be trusted to a certain extent but there are times you have to watch him.
Using personal knowledge of the DM to try to predict things which may happen, and/or saying things they think may be possibilities and trying to gauge the DM's expression to see if they're right
The players know better than to try to "read" me. I always throw unexpected things at them. In our next adventure, we're going into the Underdark. The players don't know this. They're going to end up finding a cavern entrance as part of an investigation into people going missing in an area of small towns and villages near the mountains. There are rumors to be heard about barbarians kidnapping the victims, were-rats doing the dirty deeds, etc. In one of the mining towns they shut down the mines because several miners were eaten by a "dragon" (actually a very large subterranean lizard). So they're going to think they're hunting for a dragon and end up facing a giant lizard. As they investigate further, they're going to realize that intelligent humanoids are doing the kidnapping. When they figure out the kidnappers are emerging from a cavern on the mountains, they have no idea that it's going to take them to the Underdark. They will eventually realize they're traveling deeper into the earth. And they're going to think: "
DROW!". They've been itching to have a Drow adventure and they know I love the Drow. But they believe (and I've encouraged that belief) that they're not high enough level or a big enough party (5 PCs) to face off against the Drow. And still, that's what they're going to believe. Until the clues point to the actual kidnappers - the Derro! And eventually, when they breathe that sigh of relief (though the Derro are no push-overs) and they say: "
Well thank god! At least it wasn't the Drow!", they're going to be hit with the stone cold truth - the Derro are in fact working with/for the Drow after all! Surprise!
And I've developed a tendency over the years to grin and laugh at any random time about anything. Maybe it's the Halaster name or the fact that some of my players have been hysterically paranoid, but when they see me grin and/or laugh, it can mean anything. Yes, you are in grave danger. No, you're in no danger at all but I'm getting a kick out of seeing your paranoia! Yes, the door is trapped. No, the door is not trapped and I'm laughing my ass off over your incredibly cautious attempts to safely open it. They never have a clue.
Trying to turn magic into unnecessary semantics (eg. trying to take a very specific, but not natural meaning to a geas spell or similar) rather than engaging with the story it can create (perhaps this isn't so much metagaming, but still something i don't like). It's the player version of DM's deliberately and unnecessarily screwing wishes.
I'd have to see an example of that because I'm not sure what you mean. But I don't think that's ever come up for me.
Relying on failed dice rolls to know whether what their character knows is right (eg. if the character has bad information or similar as a result of a failed roll, which naturally the player knows they failed)
Yeah, that one is tricky. I try to secretly roll dice for them when it comes to things like this. That tends to work in most cases.
Drawing on information such as things described to another character about what they feel/see that others don't (eg. maybe the character is cursed and is feeling a compulsion but the other characters don't know this). This can be dealt with by providing information separately, but that still adds a logistical challenge. Related to this, drawing on information such as if I pass a player a note or take a player off to the side to share something with them, the characters then get suspicious without basis and in the worst case have outright acted against that player's character based on that suspicion. In that case, it was a new player and thankfully the other players called them out on it.
I've been known to regularly pass along notes saying: "How are you enjoying the game?" or "What should we get to eat on break?", or lean over and whisper that into the ear of a particular player at random moments (often strategically at a point where it certainly looks like I'm passing along important info) and often. So to them, me passing a note or whispering to one player has at least as good a chance of (and usually a far greater chance of) meaning absolutely nothing than it does something.