Compile all necessary documents. You're going to need a valid passport and a U.S. driver's license. Many car rental companies will also require you to have an international license, so it is a good idea to get one of those, as well. International drivers licenses can be obtained through the American Auto Association (AAA).
Devise a budget. Gas, accommodation, highway tolls, parking fees, food and admission prices should all be included. Remember: the price of gas in Europe is a lot higher than it is in the United States, so prepare accordingly.
Create an itinerary. A good way to begin is by making a list of the places you want to see in order of priority. You can then examine the logistics of the itinerary by consulting Google Maps. Be forewarned that you might have to eliminate one or two places.
Book your flight. You will want to do this well in advance in order to get a lower rate. And, of course, it is a good idea to try and land at the first destination on your priority list (see above).
Rent a car. This can be done online in a pretty straightforward process that allows you to pick up your car directly at the airport. Alternately, every major European airport has several car rental desks with international brands such as Hertz offering immediate on-site rentals.
