Check the dipstick. Black oil isn't necessarily bad, but clear oil at least means that it's maintained to some degree. And check the level, of course.

Check the battery poles. Ideally there shouldn't be any rust on them. If the poles are greasy, the owner knows how to ensure they last for a long time.

While under the hood, Check for any rubber hoses that seem like they're crumbling

Yank one of the front wheels sideways. There should be no wiggle. If there is, you might need to replace the "steering knobs" (I have no idea what the English word for it is). None is good, a little might be OK. Loads is a problem.

Some rust on the brake disks isn't necessarily an issue. Generally, they're the parts that rust the most, and some spots generally just means that that the car has been stationary for a while. Some heavy braking will wear away these spots.

Run your finger over the brake disks. If there is no lip around the edge, they're pretty new or at least not used. Some lip is expected as the pads have worn into the disks for a while. A very big lip probably means that the brakes should be replaced (Doesn't cost much, and it's pretty easy to do yourself)