Renting a car can be an intimidating process. But, it doesn't have to be, as long as you're aware of what you should look for, and what you should ask the rental agent who services your pick-up.
Carefully Inspect The Exterior
If it's dark out, then use the flashlight on your smartphone or ask the agent for a light source. Any dents, scratches or damages you see should be marked down on the agent's sheet. It's one thing to pay for damages caused by you, but don't go paying for what someone else may have done to the car.
Check Door Handles, Windows, Wipers & Lights
Make sure to check all of the important things such as; if the door handles work as they should, if the car locks properly, if the wipers actually do their job and the lights do theirs. Roll the windows down and up, turn on the radio or other electronics and see if everything is working as it should. If the car has GPS then you may want to get familiar with it, set the language and consider asking the agent to show you how it works.
Be Aware Of The Fuel Type
Usually you choose the fuel type upon booking, but this is subject to change as everything else is. A typical car rental has many hundreds or thousands of cars in their fleet so complications can always arise which result in some deviation from your originally booked vehicle. Just open the fuel lid and check inside to see if it's a diesel, petrol or anything else.
Check The Fuel Tank
Make sure that, if the policy is Full-To-Full, the tank is actually full, otherwise the agent should be made aware and you should not be required to bring the car back with a full tank.
Get Familiar With The Dashboard, Turn Signals & Settings
Take a brief moment to go over the dashboard, make sure you're aware which gauge is for speed, which is the tachometer and which is for the fuel. Check to see if there are any warning lights, or if the temperature gauge is displaying unordinary temperature.
Make Sure The Tyres Are Seasonally Appropriate & Safe
Go over each tyre and check for shallow tread depth. If the depth is less than 1.5 mm, or worse; you can see through to the wires, then that tyre is unsafe and the car rental should replace it or the car. Is it snowing or icy? Check if the tyres are suitable for the conditions. If there's snow or ice on the roads then the tyres should be special studded or unstudded winter tyres.
Find The Nearest Fuel Station
You'll most likely be returning the car with a full tank, so as you make your way from the pick-up area, you're gonna want to keep your eye out for a fuel pump that's situated close to the car rental so that you don't burn too much between the fueling and the drop-off. If you're dropping off at the Keflavík International Airport, then you'll find a fuel station right by the car rental area, next to the terminal.
Monitor local weather reports for any hazardous or tricky weather, and make sure to use common sense. You're likely in a different country, with different laws and customs. Pay attention to other drivers on the road and keep yourself and them safe from harm.