International travel can involve extra advanced preparation. U.S. citizens should first check International Travel Information at the U.S. Department of State as well as their Tips for Traveling Abroad.
Check country specific information to find information on local customs and regulations as well as contact information to inquire about requirements for quarantine and importation of animals.
Most countries, especially rabies-free countries, follow the guidelines similar to the EU pet passport scheme which requires a minimum of six months preparation before travel to avoid quarantine. Dogs, including service dogs, must have two rabies titers as well as special paperwork and an ISO compatible microchip. Not all microchips available in the U.S. are ISO compatible, so check with your vet about yours.
For international travel it may also be helpful to contact the International Association of Assistance Dog Partners or Assistance Dogs International for additional information about international travel with a service dog.
For historical background, read IAADP's Access Issues: Quarantine Policy Changes