The safety and the comfort on the road with a rent a car are guaranteed on the base of properly selected car. You have to consider well if the car size meets your needs, think of the number of passengers,the luggage and the place that you plan to visit. If you already know how to turn on the lights, the wipers and the horn of the car is good to check where are the instructions of the car. Typically the documents are in the glove compartment.
We from sofia-rent-a-car.com/ recommend before you go to the trip to check the available washer fluid, brake fluid and motor oil. Check also if the air conditioning of the rental car is functioning well. It is good to know what will cover the insurance just in case of damage or emergency situation the way. Research and what is the phone number for roadside assistance.
You should ask what fuel use the rental car and refuel the car with the same one. When you return the car the tank should be full refueled as you received it. Otherwise you can be charged extra for refueling. Please consider well how, when and where will you return the car. It is better to do it according to the agreement, because otherwise you will need to pay extra fee for the delay.