Another tip: If the car has air conditioning/climate control you need to check that it is functioning correctly. To do this start the car if not already running, set the temperature to the lowest setting & wait a few minutes for it to blow ice cold. It might actually be better to do this on the test drive. If it doesn't blow cold it could mean a re-gas of the system or something much more expensive.
Have a look at the tyres for two things;
1. Are the tyres fitted a good recognized brand, Bridgestone, Goodyear, Michelin, Continental, etc. If there are cheapo tyres in the car it could raise questions on what other items were slumped on.
2. Have a look at the tyre thread, for two reasons:
a) Is there a decent amount of thread left? Tyres approaching the wear indicator will need replacing & you can use this in your bargaining on price
b) Check that the thread wear is even across the width of the tyre, if a tyre is worn badly on one side but fine on another it could mean wheel alignment needs to be done or wiser still that there is some further suspension work needing to be done. It could be the result of wear & tear on suspension or accident damage. Either way work & further investigation would be needed.
Airbag light, make sure this illuminates when you turn on the ignition & also goes out when the car is started. Just make sure it goes out at a different time to the oil light. I've seen where guys just hooked up the bulb to the oil light bulb because there was an expensive problem with a seat occupancy sensor.
Most cars come with 2 keys, sometimes more. Always ask how many keys the seller has. The replacement keys, especially the ones with a built in remote control can be expensive (€130-€160)
Finally don't be blinded by the car, as in get caught up in the moment, this has happened to me & sometimes it is good to have some overly cautious friend with you when viewing.
Also if you are leaving a deposit on a car be aware that in some cases this is not refundable, make sure you check up front about this (I forgot to ask this myself recently