once again, israeli security shows how it should be done.
Schneier on Security: Security Notes from All Over: Israeli Airport Security Questioning
The defender -- the terrorist trying to sneak aboard the airplane -- needs a cover story sufficiently broad to be able to respond to any line of questioning. So he might memorize the answers to several hundred questions. The attacker -- the security screener -- could ask questions scattershot, but instead concentrates his questioning along one particular line. The theory is that eventually the defender will reach the end of his memorized story, and that the attacker will then notice the subtle changes in the defender as he starts to make up answers.