On the test drive floor the car from a dead stop and see if the front wheels spin at all. When driving slowly through a parking, see if the awd system binds when you turn the steering wheel to full lock.
Other than that look for transmission shift flare, engine over heating, tiny cracks in the plastic radiator, oil dripping down onto the under tray from the oil pump and uneven wear in the tires.
Finally, make sure all four tires are on correctly and check for maintenance records!
-Chike