The longer the journey, and the more it differs from your routine driving, the more important it is to prepare carefully. If you are travelling with children or during the winter, there are special things to consider.
Traffic moves on different sides of the road in different countries. In most parts of the world, such as most of the continental Americas, continental Europe, China, the Middle East and the former Soviet Union, traffic moves on the right side of the road. However in others, most notably the United Kingdom and many former British colonies such as Ireland, Australia, New Zealand, India, South Africa and Malaysia, most smaller states and territories in the Caribbean as well as a few others such as Japan, Indonesia and Thailand, traffic moves on the left side of the road. Usually, cars in areas with right-hand traffic are left-hand drive (i.e. steering wheel on the left side), and cars in areas with left-hand traffic are right-hand drive, though there are exceptions. The arrangement of the pedals is standard worldwide.
Some countries have autonomous territories which occasionally adopt a different traffic direction from the parent country (e.g. Gibraltar (right) vs UK (left), Hong Kong and Macau (both left) vs China (right), US Virgin Islands (left) vs USA (right)). When crossing borders you may sometimes have to change the side of the road you drive on (e.g. Thailand-Cambodia border, Hong Kong-China border, Brazil-Guyana border), and the confusion may be compounded by the fact that the steering wheel is on the "wrong" side of the car after crossing the border.
It may feel awkward at first trying to drive on the opposite side of the road, and with the steering wheel on the other side from what you are used to back home, but after giving yourself time to adapt, it usually does not pose any major issues. You may also encounter road infrastructures (such as toll gates) that are designed to cater to opposite-hand driven vehicles. You may want to start driving slowly on side roads with light traffic while you adapt to driving on the other side for the first time and eventually, it will become more natural the more you drive. You may want to consider renting an automatic car, even if it is cheaper to rent a manual car, as having to adapt to operating the transmission with the other hand could be an unwelcome extra burden.
Traffic congestion is one of the most common annoyances for motorists and on many road trips it is simply unavoidable. You could however avoid the daily rush hours, weekend rush hours, days when major holidays start and end, etc., as you probably have different timetable needs from most locals.
Big events such as spectator sports and festivals can be expected to cause congestion.
In some cities driving is bound to be frustrating, as there is congestion most of the day. If there is decent public transport, finding a place to park the car and using the public transport during your stay may save your nerves and possibly also some time. When driving cross-country, avoiding cities is usually a good idea if you prefer to save time, rather than visiting them. If you do decide to visit a city, it can be a welcome change of pace to park the car at a suburban "park & ride" or other suitable parking and use public transportation during your stay in the city. Traffic planners around the globe have built "ring roads" to deal with this kind of traffic and to try and steer it around the city proper. Unfortunately, those ring roads are often the most congested roads of them all. Beijing is a particularly egregious example: it is building a seventh ring road outside the sixth ring road, which is already the longest in the world.
If you do get caught in congestion, try to keep calm. Getting annoyed or frustrated won't help anybody, while skipping the congestion on road shoulders is irresponsible (they are reserved for emergency and breakdown vehicles) and usually illegal. You can also take a break or get off the highway to explore the surrounding area — who knows, this might make for an interesting side trip or intermediate destination that you otherwise wouldn't even have considered.
Sitting for hours in a car strains both body and mind. You should get out of the seat at least every two hours, ideally more often.
When driving, truck stop or rest stops are a convenient option for stretching your legs in some Western countries. You could also plan for including suitable attractions, perhaps taking a walk to a hilltop with nice scenery. In the USA, so called stroads – highways that pass near or directly through downtown areas – offer more opportunity to avoid too much time behind the wheel, while in more densely populated regions such as the Eastern U.S., interstates serve as bypasses but with few rest stops. In Europe, bypass roads are usually faster, but you might want to stop for a café visit or just a walk in the town instead of stopping in the middle of nowhere. You could also sometimes choose a minor road and take your walk in a nice village.
Many countries require you to have a warning triangle to use in case you break down. It is not always a requirement but definitely always a good idea. Leave it at least 50 m (others say 35 yards) behind your car if you break down; on freeways, double this. This will prevent your being rear-ended or causing collisions if you have to stop in an unsafe location. A tow-rope and jumper cables are also handy. A reflective vest is useful if you break down at dusk.
See also: Automobile associations
Various motor clubs or automobile associations provide roadside assistance to members:
A membership card is issued for an annual fee. If you break down, call the number provided by the automobile association (such as *CAA or +1-800-AAA-HELP for CAA/AAA members); the motoring club usually has some existing arrangement with a local tow company at a station rate which is cheaper than what a tow company would charge if you (or worse, the police) call them directly while you are stranded at roadside.
Often, members of one automobile association can obtain roadside assistance from a partner organization in another country if a vehicle breaks down while abroad; for instance, an ADAC member could obtain AA assistance in the UK or CAA/AAA assistance in North America. The auto clubs are also a good source for maps, guidebooks, information, travel agency service, passport photos, insurance and travellers' cheques. Some hotels and hotel chains offer discounts for card-carrying members; though these are not always the best available discounts, it is always worth enquiring.
Check with the consulates of the countries you are crossing: there may be special requirements when crossing by car, for example driving from Hong Kong to mainland China requires a change of number plates at the border and a PRC-issued driving license, In some cases, crossing borders will require you to change the side of the road you drive on (e.g. Hong Kong/mainland China, Thailand/Laos, or UK/mainland Europe).
Some countries (including Mexico) impose specific requirements for customs documents (such as a Carnet de Passage) to prove that a temporarily-imported vehicle will be taken out of the country at the end of a trip. Insurance requirements also differ between countries; don't assume that cover which is valid at home will be honored abroad (Canadian insurance policies usually are valid in the US, but a US/Canada insurance is most likely worthless in Mexico). Even if the policy is valid in the country to which you intend to travel, there may be a higher minimum amount of liability coverage in another jurisdiction or a requirement to carry a specific document in-vehicle as proof of valid insurance. In some countries, the wealthy foreigner is at high risk of being found at fault in any collision.
A rental car firm may refuse to allow their vehicles to be driven to another country (with restrictions prohibiting operation of western Europe hire cars in eastern Europe or US hire cars in Mexico being common; Argentina does not permit rental cars to leave the country at all).
Related: Renting a car