Your age, age restrictions vary from country to country and even among suppliers in the same country, - some suppliers won't let you rent if your age doesn't meet the requirements while some will charge a young driver fee
Is your national driving license valid in the country of rental? in case your driving license is not in roman letters International driving permit is mandatory.
Will you drive out of the country where you rented a car? Check out the driving permissions, usually it is permitted to drive within EU, however different companies might have certain restrictions specially when driving from EU to Croatia, Serbia, Montenegro…
Do you want to return the car in another country? it is not for free. Always make sure to acquire the cost of international one way rental. Costs may vary from 100 Eur up to 1000 and more ( the distant the country, more expensive it gets
Fuel policy - pick up full return full – in this case you have to take care of full tank in return, otherwise you will pay a separate cost of fuel, some companies will include the cost of fuel in the price in this case you have to return empty tank – always check fuel policy
Will you order anything else - like GPS, baby seat, ski rack? - Those items are always charged additionally
Read your vouchers – voucher contain all the necessary information about terms and conditions, location address, additional extras and other information crucial for customer. Read them.
Do you need a manual or automatic transmission? In Europe manual transmission is more popular and widely used, therefore automatic cars are slightly more expensive.
Time of pick up and return – you have to know that if your return time is later than your pick up every car rental company will charge you another day. Think about your arrival and choose hours that will eliminate this cost if you can.