This applies to US residents.
You lose your passport
To get a new passport, you need to go in person to a U.S. embassy or consulate. Visit travel.state.gov or call 202/ 501-4444 to find the location nearest you. Here's where that photocopy of your passport everyone recommended comes to the rescue. (Don't have one? Get a copy made now. No, really--now. And pack it separately from your passport.) The photocopy, along with a driver's license or other ID, should be acceptable proof. If you're scheduled to depart within 14 days, you can get an emergency passport on the spot, valid for up to a year. Standard passports valid for 10 years can also be issued abroad, but the process takes about two weeks. For someone in the U.S., getting a passport issued within 14 days costs $157. But somehow, if you're in another country, the cost is only $97 for either an emergency or a standard passport. Travelers without a passport photocopy or any ID will need to prove their citizenship, which will probably take a few days. And everyone applying for a passport abroad must visit an office during regular business hours. In the past, when an embassy was closed, an officer could write a "transportation letter" to try and get you on the plane. After 9/11, that no longer happens. Missing a flight is not a big enough emergency for exceptions to be made.
You're sick--really sick
Some health plans, such as Medicare, offer no coverage outside the U.S.; others will reimburse you for payments made out of pocket (Aetna is one); and still others may pay foreign hospitals directly if you arrange this in advance or upon admittance (Blue Cross/Blue Shield). Remember that 800 numbers often don't work overseas, so keep your insurer's local number handy. Depending on your plan, or lack thereof, consider travel insurance. Compare options at insuremytrip.com, and read the fine print carefully. If you have no coverage and are critically injured, the local U.S. embassy can arrange to send you home, at your expense. Read up on your destination's health-care system and health threats at travel.state.gov.
Your wallet is stolen
First, cancel your credit and debit cards. The maximum you'll have to pay for unauthorized charges is $50 per credit card, but you'd be wise to try and cancel before any purchases are made. Every credit card company has a 24-hour hotline that accepts collect calls. Cash advances and replacement cards won't be available immediately--one more reason why you shouldn't keep all your cash and valuables in the same place. Hiding a few $100 bills or traveler's checks in a separate bag, your shoe, or several different spots is a good idea. File a police report--if not in the hopes of recovering your wallet, then because it'll help with insurance claims and at airport check-ins. If you're traveling within the U.S. and have no photo ID, call and tell the airline about your predicament. Airline staff know that getting a duplicate license may take weeks, and can allow you onto a flight without photo ID. Show up ahead of time for additional screening, and bring a copy of the police report and any ID you still have.
Your luggage is damaged, or worse
File a report with the airline for damaged bags within 24 hours of arrival, or your claim could be dismissed. Airlines generally pay compensation for bags (and any damaged items inside) when luggage is torn or dented in transit, but can refuse to pay when there's no external damage. (Pack fragile items very carefully in checked bags, or better yet, keep them in your carry-on. Mailing some items might be smarter.) If luggage is destroyed or completely lost, you must list all the items inside to get reimbursed, as you would on an insurance form for a burglary. Airlines pay a maximum of $2,800 per passenger for lost luggage on domestic flights, though each carrier's policy is a little different (many exclude coverage of jewelry, camera equipment, and medications). In 98 percent of "lost" luggage situations, bags are eventually recovered. When delays occur, airlines may advance passengers cash or reimburse them for necessary items, such as toiletries and a change of clothes. (Ask how to proceed before leaving the airport; you'll need to fill out forms and perhaps keep receipts.) The airline will pay for shipping delayed bags to passengers, even if they're at a resort five hours from the airport. Always label your bags clearly.
The flight is canceled, or you're bumped
When a flight is canceled, the airline is responsible for getting passengers on its next departure with open seats. Waiting at the airport counter isn't the only option--calling the airline's 800 number is often a quicker way to rebook. Some carriers put stranded passengers onto competitors' flights, though they're not required to do so. They're also not required to provide snacks, bottled water, or lodging unless delays last a certain period of time (generally a minimum of four hours). Most airlines make efforts to ease the pain of waiting, but they do so on a case-by-case basis. As for overbooking, the Department of Transportation requires compensation for passengers who relinquish seats voluntarily. There's no federal standard for that compensation--you're only guaranteed something, usually a flight voucher. For passengers who are involuntarily bumped on domestic flights, the rules are as follows: If you're on another flight within an hour, you get nothing; within two hours, the airline pays you the equivalent of your one-way fare ($200 max); more than two hours later, you get 200 percent reimbursement ($400 max).
You're in trouble with the law
A third of the 2,500 reported annual arrests of U.S. citizens abroad are drug-related. To avoid trouble, do the obvious: Just say no, and never leave bags unattended. Familiarity with local laws is essential, especially in strict countries. In Turkey, all "antiquities" are owned by the state, and trying to bring home a souvenir that's a few centuries old could land you behind bars for a month. During any run-in with the law, be respectful and apologetic. If you're locked up, actively request that local authorities inform the U.S. embassy, which, according to the Vienna Convention on Consular Relations, must then happen "without delay." A consular officer can visit you, provide contact info for local attorneys, fill you in on the basics of the local legal system, and inform your loved ones of the situation.