Brakes-male sure their not making noise and the rotors are not all scratched up
No noise from the suspension going over bumps
Then for a particular model of car, research the common problems. Like if the water pump is known to go bad at ~100,00 miles and the car has 95k on it, try to see if it has been replaced recently
Most things aren't deal breakers and you can just fix them after you buy it, but that cost of repairs should be taken off the buying price imo