I'm with Ozmar.
If a character is trying to do something that may be stupid, I make sure I've communicated all the details necessary for them to make an informed decision. Even then, I'll offer 'common sense' hints for obvious things, or Int or Wis checks for more subtle things.
Metagame thinking goes both ways... the player may know things that the character wouldn't, and the character would know things that the player wouldn't. It's difficult to communicate enough detail of the game world without accidentally throwing red herrings or giving away too much (the old 'if the DM said it it's important' thing).
For instance, my group was tailing a small group of chanting cultists across a rather flat, open moor. When the Wizard wanted to cast a spell, I let him know that even though the spongy, dank ground seemed to dampen sound, there was a decent chance the cultists would hear the verbal components since there was no other sound. Hey, 22 Int. When the rather dim (8 Int) Paladin was pushed to the front to do some Diplomacy with a doorman later, and the player had to respond with a code word (that I dropped on them in an obvious way earlier), I made him roll a check to see if I would give him the hint. He failed. Combat ensued.
The idea I run with is to balance the player's and character's knowledge so that things make sense. Would a 5th level wizard be able to judge a Fireball perfectly? Depends, but in a difficult situation he risks blowing it. Would an 18th level wizard? Absolutely, and I'd tell him extra things that weren't immediately obvious if I felt the (extremely experienced and knowledgeable) character would know.