Be sure you have the car rental company's phone number – most of the companies have a 24/7 service number.
This will prevent unwanted issues, and will save you time and money. If you're unsure, ask regarding driving conditions for your destination – you can ask the rental company, people you know or search on the internet.
Make sure all of the dents and scratches on the car are documented before you sign the rental forms. You should also make sure that everything is working properly, such as the air conditioner, heating and lights. Report any problems which are not listed. Remember that from the moment you sign you are responsible for the car, including its damages.
This is especially important during high season when there are many people and long lines. In most cases, it is recommended to get insurance which can save you money in the long run. However, you should not get insurance which is irrelevant to you, such as insurance for young drivers which costs more in certain companies.
Don't forget to fill the gas tank before returning the car. This will save you extra fuel and service fees.
Avoid this if possible. In certain countries, using vehicles with diesel engines will be significantly cheaper than using vehicles that run on gasoline. Return the car on time to avoid stress and extra fees that are incurred with a late return. It's important to take enough of a buffer in unfamiliar places.