Here's what I would look at:
Make sure all the electonics, windows and sunroof work properly.
Visual check of engine components to make sure there isnt any leaks.
To see the car's true colors it needs to go up on the lift so you can check whether anything is leaking: transmission, oil, coolant..etc.
Check the brakes and tires.
Test drive and make sure it shifts smoothly.
Best thing you can do is hire a mechanic to come with you, spend a few bucks extra to know exactly what your getting.