The sine qua non of international travel is a valid passport, which along with health insurance identification should be kept on or near one's person--and thus not in checked luggage--at all times. Acquiring a U.S. passport can take ten weeks or more; the Department of State recommends that applicants "expedite" the process if traveling in less than ten weeks.

Thoughtful packing can forestall minor catastrophes and promote personal comfort while on tour. Basic toiletries and a change of clothes should be packed in the carry-on bag--along with passport and medications--in case checked luggage goes missing. Comfortable footwear is essential. Most experienced travelers dress casually and in layers.

An excellent companion on tour, and a good source of information beforehand, is a standard guide like those published by the Frommer, Fodor, or (better yet) the Lonely Planet and Rough guides. These will include maps, historical information, and advice on money, restaurants, and the productive use of free time.

The Department of State offers useful information, including details on applying for a passport: visit travel.state.gov.