1. Check for any user marks. User marks on hot area like flash, lens or tripod mounting area are fine. Other places you may need to investigate closely. The camera might be banged to some hard material or dropped to cause the mark.
2. Check dead pixels.
3. Check for sensor dust. Take photo with long exposure with minimum aperture. All dust will come out under white background.
4. Check battery life if it is still in the condition per stated.
5. Press all buttons and common dials, they should not be sticky nor abnormal.
6. If warranty is still applied, check if the serial number on the camera and warranty card is matched.
1. Check for user marks. Optics should be cleared.
2. If it has aperture ring, tune to max aperture, and observe the dust under bright light.
3. Check MF, AF, VR etc button if they are functioned well.
4. Check sharpness at different zoom range.
5. If warranty is still applied, check if the serial number on the lens and warranty card is matched.