A tourist card is required for all Americans traveling to Mexico, and if arriving by air, Americans must also carry a valid passport. Minors traveling with one parent need notarized permission from the absent parent. You'll be given a tourist card application form on your flight; the cost of around $20 is usually included in the price of your airline ticket. You're supposed to keep a portion of the form. Just fold it in half and keep it safely inside your passport. And be sure that you do. You'll be asked to hand it, your ticket, and your passport to airline representatives at the gate when boarding for departure. Not having your tourist-visa documentation will be a problem; both time-consuming and costly, replacing it costs more than $25.

Passports

A passport verifies both your identity and nationality—a great reason to have one. Another reason is that you need a passport now more than ever. At this writing, U.S. citizens must have a passport when traveling by air between the United States and several destinations for which other forms of identification (e.g., a driver's license and a birth certificate) were once sufficient. These destinations include Mexico, Canada, Bermuda, and the Caribbean (except the territories of Puerto Rico and the U.S. Virgin Islands). Soon enough you'll need a passport when traveling between the United States and such destinations by land and sea, too.

Another law, passed in early 2008, now requires that U.S. citizens provide both proof of citizenship and identity when returning to the U.S. by land or sea ports. A passport will cover this, as will a birth certificate paired with a driver's license, but for a complete list of the forms of citizenship and identification that will qualify, see www.cbp.gov.Children under 18 are only required to provide proof of citizenship.

U.S. passports are valid for 10 years. You must apply in person if you're getting a passport for the first time; if your previous passport was lost, stolen, or damaged; or if your previous passport has expired and was issued more than 15 years ago or when you were under 16. All children under 18 must appear in person to apply for or renew a passport. Both parents must accompany any child under 14 (or send a notarized statement with their permission) and provide proof of their relationship to the child.

Before your trip, make two copies of your passport's data page (one for someone at home and another for you to carry separately). Or scan the page and e-mail it to someone at home and/or yourself.

There are 13 regional passport agencies, as well as 9,000 passport acceptance facilities in post offices, public libraries, and other governmental offices. If you're renewing a passport, you can do so by mail. Forms are available at passport acceptance facilities and online.

The cost to apply for a new passport is $100 for adults, $85 for children under 16; renewals are $75. Allow six weeks for processing, both for first-time passports and renewals. For an expediting fee of $60 you can reduce this time to about two weeks. If your trip is less than two weeks away, you can get a passport even more rapidly by going to a passport office with the necessary documentation. Private expediters can get things done in as little as 48 hours, but charge hefty fees for their services.

Visas

A visa is essentially formal permission to enter a country. Visas allow countries to keep track of you and other visitors—and generate revenue (from application fees). You always need a visa to enter a foreign country; however, many countries routinely issue tourist visas on arrival, particularly to U.S. citizens. When your passport is stamped or scanned in the immigration line, you're actually being issued a visa. Sometimes you have to stand in a separate line and pay a small fee to get your stamp before going through immigration, but you can still do this at the airport on arrival.

Getting a visa isn't always that easy. Some countries require that you arrange for one in advance of your trip. There's usually—but not always—a fee involved, and said fee may be nominal ($10 or less) or substantial ($100 or more).

If you must apply for a visa in advance, you can usually do it in person or by mail. When you apply by mail, you send your passport to a designated consulate, where your passport will be examined and the visa issued. Expediters—usually the same ones who handle expedited passport applications—can do all the work of obtaining your visa for you; however, there's always an additional cost (often more than $50 per visa).

Most visas limit you to a single trip—basically during the actual dates of your planned vacation. Other visas allow you to visit as many times as you wish for a specific period of time. Remember that requirements change, sometimes at the drop of a hat, and the burden is on you to make sure that you have the appropriate visas. Otherwise, you'll be turned away at the airport or, worse, deported after you arrive in the country. No company or travel insurer gives refunds if your travel plans are disrupted because you didn't have the correct visa.

U.S. Passport Information

U.S. Department of State (877/487-2778. travel.state.gov/passport).

U.S. Passport & Visa Expediters

A. Briggs Passport & Visa Expeditors (800/806-0581 or 202/338-0111. www.abriggs.com). American Passport Express (800/455-5166 or 800/841-6778. www.americanpassport.com). Passport Express (800/362-8196. www.passportexpress.com). Travel Document Systems (800/874-5100 or 202/638-3800. www.traveldocs.com). Travel the World Visas (866/886-8472 or 301/495-7700. www.world-visa.com).