As a trivial random encounter is winding down, a player thinks “That was too easy… The GM wouldn’t give us an encounter that doesn’t give XP,” and starts searching for hidden bad guys or other clues.
There are four statues in a room, and you use miniatures to represent them. The players think to themselves “Well if the GM used miniatures, these things are definitely coming to life,” and get ready to fight.
When you lay down a map of a seemingly random part of the forest trail, the players think “This must be important, let’s search around / prepare for battle.”
You roll a 1 for a player’s knowledge check and feed them inaccurate information. They saw the roll and know you’re full of it.
Even the most disciplined players sometimes will take advantage of “Player Knowledge” over “Character knowledge.” Sometimes it’s hard to even tell the difference. You know that you should switch to your frost battleaxe against that Fire Demon, but does your city-raised fighter with the intelligence of an old boot know?
What strategies are there to discourage the use of player knowledge, and how can you cut back on perceptions that players have of the genre itself?