One of the basic principles of roleplaying is that players should not use OOC (out of character) knowledge to make IC (in character) decisions. What is known to a player might not be known to his or her character, and a character can not make decisions based on information he or she does not know.
Unfortunately, GMs and players often try to over-simplify dealing with OOC knowledge. In doing so, they destroy any chance a player's character will make a good decision and force them to make bad decisions. For example: suppose a player is playing a medieval fantasy game and his or her character is exploring an enemy castle. If the character encounters a hallway that is unguarded and appears perfectly unremarkable, the player might realize the situation is too convenient and try tossing some rocks down the hallway in hopes that they will set off any traps. However, if the player has somehow OOCly learned that there is a trap in the hallway, then he or she will probably be accused of cheating upon tossing the rocks or doing anything other than walking down the hallway and falling victim to the trap.
So, how should useful OOC knowledge be handled? One good way might be to use dice. Roll the dice to determine if the character makes a good choice or a bad one.