You should also educate yourself on the laws in different countries governing driving. For instance, in Mexico it's legal to drive, but illegal to get into an accident; the typical way to treat an accident is to exchange information as quickly as possible with the other driver and then drive away before the police get there. Again, AAA and similar organizations can tell you about these sometimes surprising differences.
Differing Opinions on Car Maintenance
Especially if you're planning to rent a car in a third-world country, you'll find that the US has somewhat luxurious notions as to how a car should be maintained. In order to save money on gas, there are taxis in India that run mostly on propane tanks stored in the trunk. In Mexico and most of Africa, it's wise to be a mechanic before driving outside a city.
If you rent a car from an internationally recognized company such as Hertz or Enterprise, you should have much better luck, but you should also be ready to pay a pretty penny for the privilege. Rates of theft and carjacking in many countries are considerably higher than in the US, and companies that rent nice cars also incur more expense from the loss of these cars. However, a bargain car from a local rental agency may not be a bargain at all.
Emergency Roadside Assistance
In some countries, emergency roadside assistance simply does not exist. In India throughout most of the country you are not likely to find much in the way of help if you are in an accident out in the countryside. When in a country with standards you're unfamiliar with, educate yourself as completely as possible on your planned driving route, and don't deviate from it. Check on the country's emergency assistance number; 911 only works in the US. Find out if your roadside assistance policy works in the country you're traveling to, and double-check that your cell phone will work along your route as well.
Traveling by yourself in a foreign country can be very exciting, but it can also be very dangerous if you have an emergency. Above all, be prepared for anything.
In the US, gas prices have increased quite a lot in recent months, but they still aren't a match for the prices in many foreign countries. For example, in many European countries a liter of gas may cost you the US equivalent of about a dollar and a half -- converted to US gallons, this is over six dollars! Taxes on international rentals, toll roads, and similar expenses may add up more quickly than you anticipate. Be prepared for this sort of cost when you rent your car, and ask at the rental office what you should expect in the way of these things.