Where does one obtain foreign policy experience?

It has always been said that governors make the best presidents of the United States. As has been mentioned in the media and elsewhwere most of the past recent POTUS have been governors of states. This will be the first time in a number of years (JFK) that we will have a U.S. senator for a president. One of the issues that seems to always come up is "foreign policy experience". This seems to be the issue that makes Palin unfit to be president. But my question is this. How can a person who has "only" been a governor of a state receive foreign policy experience? How much experience in this area did Bill Clinton have before getting elected?
How about Reagan? Carter? Bush? Does a person have to know the location of every country on the globe and its leaders before it is said that the individual has enough knowledge of foreign affairs to qualify to run the country? Where does a governor of a state obtain the expertise that is required to handle something like 9/11? North Korea? Georgia and Russia? China?