Carfax and service records (oil change and maintenance receipts in particular) are a must. See how recently the last service was completed. Check the tire tread life, since a set of tires can add more to your overhead, especially as the tire sizes go up. Make sure all of the tires are of the same make and model. Make sure the wheels aren't curbed. Compare the mileage to the model year of the car, so if the car is a 2005 and has 50k miles, then it's been driven a ton and will have more wear and tear on it. (Don't believe that crap about how it's "all highway mileage," miles are miles no matter where you are.) Check the condition of the interior, since cloth tends to wear out, and leather can begin to crack. Cloth can also absorb unpleasant odors over time. Make sure the owners manuals are in the glovebox and the tire changing tools are all there.
When taking it for a spin, make sure all the windows work properly and the A/C runs. Press the brake pedal, and if the pedal goes pretty far in, it may need new brake pads. Same thing with the E-brake, if you pull it and it goes pretty far up, the rear brake pads may need to be changed.