Check the oil; it should be translucent brown, not black or milky white. Look at the coolant and brake fluid levels as well.
The cabin's condition often reflects how the car was treated overall. What to Look for When Buying a Car: A Complete Guide check car before you buy
Look for mismatched paint or uneven gaps between panels (like the hood and fenders), which often signal previous accident repairs. Check the oil; it should be translucent brown,