Car rental companies such as Avis, Budget, easyCar.com - click here, and Hertz have offices in most Andalucian cities and at the major airports of Malaga and Seville. The rates of major international companies vary little, although you may get a better deal by booking in advance. However, the smaller local rental companies tend to be less expensive. If you're a visitor, it's advisable to reserve a rental car before arriving, particularly during peak periods.
When comparing rates, check that prices are fully inclusive of insurance and taxes and that there are no hidden costs. Policy on payment for petrol varies - check the small print. Most issue cars with a full/half/empty tank and ask you to return the car the same. Others charge for a full tank and do not credit you when the car is not returned empty.
Some companies don't offer unlimited kilometres which will work out more costly unless you plan to just do a few kilometres which is difficult in a region as vast as Andalucia. If required, check in advance that you're permitted to take the car out of Spain, such as to nearby Portugal or Morocco. This is usually prohibited.
To rent a car in Spain you must produce a valid licence (a copy is not acceptable) and sometimes a passport as well. If more than one person will be driving, all the drivers' names must be included on the rental agreement. Check in advance about insurance cover for young drivers under 26 or 22. Credit cards are commonly used as a deposit. If a credit card isn't used, there's usually a high cash deposit.