Hilzoy lists them. These two strike very close to home in my case:
(4) When the rest of the world thinks you're crazy, it's worth entertaining the possibility that they might be right. We should not defer to their judgment mindlessly, but we should have what Jefferson called "a decent respect to the opinions of mankind."
(5) Beware of movements built on contempt. Many of the people who pushed for war had spent decades expressing their contempt for what you might call standard foreign policy -- the kind in which diplomacy is taken to be a useful instrument, not a snare for the weak-minded, and force is a last resort, not an all-purpose tool. Their own views had never been seriously tested (and no, Reagan doesn't count), and many of their spokesmen lacked any serious experience conducting foreign policy. Sometimes, groups of people who spend years muttering about how different things would be if they were in charge are right. Often, however, they are not. Absent a real track record on which to evaluate them, they should be approached with caution.