We use a variant on the Common Sense advantage from Thomas Barnes, at
http://www.thecabal.org/gurps/rareitems/comsense.html.  In brief:



You can set aside your emotions and desires to look carefully at the facts of any situation. You re good at figuring out "the right thing
to do" and the prudent course to take.

You have +4 to IQ to figure out "the right thing to do" in a given situation based on the facts you have at hand. If the character makes
his roll vs. IQ +4 the GM must give the player his best assessment of what the character ought to do given the facts the character
knows. If the GM feels that it is important that a character do something (or not do something) then he can roll vs.. the character's
IQ+4. If the roll is successful, the GM can tell the character's player "what common sense would dictate" in a given situation.

Characters with Common Sense also get +1 to Will to resist their mental disadvantages when they know that it would be socially
disruptive or dangerous.

For example, a character with Common Sense and the Lechery disadvantage would get +1 to his Will to avoid making a pass at the
Queen or his best friend's wife. He would also get a +1 to Will to avoid following an attractive but fey lady down a dark alley in the
rough section of town. He wouldn't get the +1 to Will to avoid dalliances in other situations. (However, you can be damned sure that
he will be careful to take precautions to avoid disease and pregnancy, or at least cover his tracks.)

In some situations where the character has a chance to demonstrate his wisdom, the GM can give the character a free +1 Reputation
for Prudent Judgment among the people who know him. (This is especially appropriate if the character doesn't have any
Will-dependent mental disadvantages.) The character will be sought out as an investigator, arbitrator, and/or judge by his friends and
associates.