1st, check the physical look of the cam, see whether got any scratches or conditions of the cam.
2nd check the surface for the lens, then LCD and any LCD display
(look for scratches and etc)
3rd check for the lens, see whether got dust inside the lens or not. (hard to say, last time one ***** co's product got dust inside, brand new one!)
4th Check the serial number of the cam , see whether match the number on the warranty card and the box
(many buyers miss this part)
5th Try to take some pictures with lens cap attach at some certain settings e.g.: ISO 100 or 200, shutter speed 1/4, 1/8 , 1/2 , 1 second to check for the deadpixels/stuckpixels or even noises (hotpixels). *note that under the ISO400 or 800 the noise will be relatively high.
6th Take out different colour papers e.g: pure yellow, pure red or pure blue. Take some pictures just base on these cards or papers. Then display on the LCD or viewfinder screen. See whether got any pixel that cannot display the colours. This is a deadpixel, if it cannot display the colour. Afterall, the 5th method can be used.
7th Try to connect to the TV there and check for the deadpixels and hotpixels. (make sure the hotpixels only in an acceptable limit) by enlarging the pictures largest possible and use the control button to toggle .
8th Immediately (or you have a laptop), right after you bought your DC, take the pictures using the 5ht method with the lens cap on and use software to analysis. Under high ISO, the noise will be obvious but should be under acceptable level.
9th If got any problem, go back for exchange and go through method 1 to 8 again.
haha... I was so keen in getting my Nikon 4500 that when I got a good price from AP, I almost forgot to check the camera before swiping my card.... haha.... just careless... eventually did and loved the feel of it... nice, cant wait to actually go around taking pictures with it... =)
So always remember to check everything swee swee before buying...!!!