This might be a broad topic, so let me focus on one scenario, where I would like to hear which actions and methods fellow GMs use.
A fantasy campaign runs along. BLUE plays a character who is dumb as a door, but good at fighting. The mechanics of the game reward player with combat techniques and lots of hitpoint, but mark out that the character simply isn't very bright.
GREEN chooses to play a bardic character, wise in the ways of the world, and witty as the day is long, but clearly no match compared to BLUE.
Now, in real life, BLUE is a well read fan of literature and the game lore, where GREEN isn't that strong on reading in person, but is a good chap around the table.
GM has prepared a series of riddles and clues, and explains these to the players. BLUE quickly figures out the answers to these, and sort of blurts them out. This happens from time to time, and puts me in a bit of a bend, because the riddles were meant to be "for" GREEN, while BLUE does the muscle work.
And here is my question. Of course, skills like swordplay or running fast won't be carried into the game itself, since were playing tabletop, but out-of-game skills that players carry can easily make a character figure out things, they wouldn't normally figure out themselves.
How do you bar real world skills from throwing the party synergy out of balance?
And as the GM, I don't want to hide the riddle behind the rules and go "The villain says a riddle, roll Wisdom to solve it."
Riddles are just the most common place where it's obvious that skills shine through. But it also carries a great deal in the plot as a whole, if the players feel who is going to backstab them, who might be telling lies, and generally seeing the bigger picture.
How do you convince the characters to hold information back, when figuring stuff out is clearly the advantage to the group. Once said out loud, it's too late for the GM to say "No no, GREENs character needs to figure this one out himself..."
Both game mechanical, social and psychological solutions are welcome.