Make sure you have a signed, valid passport (and visas, if required). Also, before you go, fill in the emergency information page of your passport!
Read the Consular Information Sheets (and Public Announcements or Travel Warnings, if applicable) for the countries you plan to visit. (See “Consular Information Program” section for more details.)
Familiarize yourself with local laws and customs of the countries to which you are traveling. Remember, the U.S. Constitution does not follow you! While in a foreign country, you are subject to its laws.
Make 2 copies of your passport identification page. This will facilitate replacement if your passport is lost or stolen. Leave one copy at home with friends or relatives. Carry the other with you in a separate place from your passport.
Leave a copy of your itinerary with family or friends at home so that you can be contacted in case of an emergency.
Do not leave your luggage unattended in public areas. Do not accept packages from strangers.
If you plan to stay abroad for more than two weeks, upon arrival you should notify by phone or register in person with the U.S. embassy in the country you are visiting. This will facilitate communication in case someone contacts the embassy looking for you.
To avoid being a target of crime, try not to wear conspicuous clothing and expensive jewelry and do not carry excessive amounts of money or unnecessary credit cards.
In order to avoid violating local laws, deal only with authorized agents when you exchange money or purchase art or antiques.
If you get into trouble, contact the nearest U.S. embassy.