“Throw the keys through the kiosk’s open window. We’ll get the car when we open later”: Those slightly unorthodox drop-off instructions I once received from a Hertz manager in Croatia illustrate some of the differences U.S. travelers might encounter when renting a car abroad.

It pays to familiarize yourself with the local policies and protocols ahead of time. Here’s what you need to know before you accept the keys.

You may need an international driver’s license

If you have a U.S. driver’s license, an international driving permit is officially required (along with your state-issued license) in Australia, Austria, Bulgaria, the Czech Republic, Estonia, Italy, Japan, Poland, Romania, Serbia, Slovenia, Slovakia, Spain and Thailand, although its use is not universally enforced. It’s also a good idea to carry an I.D.P., a booklet — slightly bigger than a passport — that translates a U.S. license into 10 languages, when renting a vehicle in a country whose language is not written in Roman letters.

An I.D.P. costs $20, is valid for one year and is issued to any applicant by a local AAA office (the only issuer in the United States authorized by the State Department). You must apply for one in the country that issued your regular driver’s license.

Familiar brands may be franchisees

Car rental brands familiar to Americans operate throughout the world; those include Alamo, Avis, Hertz, National, Sixt and others. You can reserve a vehicle through a company’s U.S. website or through a rental aggregator such as Autoeurope.com, to compare rates.

The overseas branches of U.S. companies may not always be owned by the parent company. The discussion boards on websites like Tripadvisor abound with commenters calling out franchise operations of major chains for not providing the service they expect from a U.S. operation.

Franchise or not, disputes with a foreign branch should always be directed to the U.S. customer service operation, according to Hertz and Autoeurope.

Check minimum (and maximum) age requirements

The minimum age to rent a car varies by country and company, and it’s indicated on each rental agency’s website. Most countries charge a “young driver” surcharge for renters under 25. Some countries, such as France and Germany, allow (but do not require) companies to rent to 18-year-olds, but 21 is the typical minimum rental age for most.

At the other end of the spectrum, Hertz won’t rent a vehicle in Northern Ireland to anyone older than 79; those from 75 to 79 must have a doctor’s letter stating that they are in good health, as well as a letter from their insurance company proving that they haven’t had an accident within the past five years.

Cut costs with a stick shift

Cars with manual transmissions are still popular in many European countries, so if you’re comfortable driving one, select that option. Renting a car with an automatic transmission can typically cost an additional 30 percent or more.

Check your credit card’s rental insurance coverage

Many U.S.-issued credit cards cover damage to your international rental car if you’re in an accident, as long as you charge the entire rental fee to the card. Some issuers also require that the same card be used to make the reservation for the insurance to be valid. That collision coverage is primary, unlike in the United States, where your personal vehicle insurance would cover the costs while your rental insurance would pay for any deductible amount. Even if your credit card covers damage to your rental vehicle, you will be responsible for the cost of damage to any other vehicle if the accident is deemed to be your fault.

Be warned that standard rental insurance for American Express cardholders is not available in Australia, Italy and New Zealand, and other cards may have different restrictions.

Familiarize yourself with local driving and parking laws

Before you go, learn each country’s rules, including the meaning of various road signs and markings. For instance, simply because you see other vehicles parked with their wheels on the sidewalk — common in European cities with narrow streets — that does not mean that it’s legal to do so.

Autoeurope.com has driving tips for dozens of countries, not all in Europe, and Britain’s Automobile Association lists road rules for six European countries. Don’t forget that many places besides Britain drive on the left (including Japan, Australia, New Zealand, South Africa and numerous Caribbean islands). And if you get a ticket, don’t ignore it. The rental agency will eventually collect from you, along with an administrative fee.

Seatbelt laws are often strictly enforced, with a separate fine — sometimes issued on the spot — for each occupant not wearing one.

Finally, many European cities restrict driving in central or historic areas to residents only or those driving low-emission vehicles. Entering these limited-traffic zone areas can incur heavy fines, plus an added fee from your rental company. Watch for signs and gates (commonly marked “ZTL” in Italy).

Know your fuels

Diesel engines are very common in other countries; putting diesel in a gas engine or vice versa can cause serious — and costly — damage.

While fuel pumps are color-coded to indicate what they dispense, those colors vary by country and region. Fuel requirements are listed on a sticker on the inside of the filler door.

In the United States, black indicates gasoline while green designates diesel. In Iceland and other European countries, it’s the opposite: green for gasoline and black for diesel.