Apply early for a passport, or renew your old one. It should be valid for at least six months after you return home, and needs to have two or more blank pages. Otherwise, some countries may not let you enter. Check all family members’ passports because those for adults are valid for 10 years, but children’s passports only for five. U.S. citizens must use a U.S. passport to leave and come back to the United States.
If you are traveling by land or sea, you must show proof of both your U.S. citizenship and your identity when you return to the United States. For many land or sea trips, this means you can travel using the new U.S. passport card instead of a normal passport book. Read more about U.S. passport requirements.
Get a letter from your doctor for medications you are bringing. Some countries have strict laws, even against over-the-counter medications, so read about your destination before you go.
If you are traveling alone with children, foreign border officials may require custody documents or written consent from the other parent. Check with the embassy of your foreign destination before traveling.
Make two photocopies of all your travel documents in case of emergency. Leave one copy with a trusted friend or relative at home and carry the other separately from your documents in case of loss or theft.