Book in advance. Rental rates are almost always higher at the counter than they will be over the phone, even just 24 hours before pickup. If you have time, comparison shop. Visit the Web sites of several rental agencies and search for identical cars on your travel dates.Whenever possible, make all car rental arrangements, from booking to payment, before you leave the United States. Doing it this way almost always makes the process cheaper, easier, safer and less likely to include hidden clauses. Once you are overseas, shifting exchange rates, unfamiliar rental specs, language barriers and other cultural differences can cause unexpected problems.
Ask about weekend specials, late penalties and gas charges. Many hidden discounts or additional costs will not be explained at the time of rental, and it may be too late once you find out.
Ask what time a car is expected for drop-off. Many rental agencies begin charging for each 24 hours from the time of rental, and will bill a full day for cars returned after another 24-hour period begins.

Be aware that many countries have a minimum and maximum age for renters. Drivers under 25 or over 70 may face surcharges or not be permitted to rent at all.Whenever possible, if you see an ad for a special rate, clip the ad or write down the promotional code. Many of the best rates do not show up on agents' computer screens without a little prompting.

Always ask about senior citizen, AAA, credit card and frequent flyer program discounts or add-on offers.When making reservations for car rental pickups at an airport, choose a smaller car than you would typically desire. Airport fleets are often stocked with larger cars, as they are primarily used by business travelers, and you will often receive a free upgrade from a subcompact booking. Be aware, however, that European cars tend to be smaller than their American counterparts; while this might be useful if you're planning on driving on narrow country roads, it's not so great for those who are extra-tall, carrying a lot of luggage, or traveling with a family or large group. In those cases, don't take a risk -- be sure to order the size you need just in case you don't get an upgrade.
Most European cars have manual transmissions -- although automatic cars can be found, often at a price. If you can drive a stick shift, it could save you money and hassles, but don't forget that you will probably have to share driving chores. Driving in Europe is often more strenuous than driving in the United States, as back roads and even some highways tend to be hilly, winding and often precariously placed on a mountainside or ocean cliff. Don't expect one person to do all the driving -- so if not everyone can drive a manual transmission, consider looking for an automatic. Also, if you're going to a country like England or Ireland, be sure everyone's comfortable with driving on the left side of the road.

Thanks for the great tips, very useful. I think renting cars in a different area should be researched before you do it. Because everyone's policies are fairly different.

it's wise to book online, but the best is to book as early as possible in order to get the lowest rate.
harry

Absolutely agree with Sacback! I always book, rent and buy everything in advance when I travel abroad!
Cars (usually when going to Europe I rent from Europcar.), Travel Phones (I always use the service provided by CallinEurope), Hotels (Depending on the destination)
My slogan is: Fell sure and secure in any country!