In addition to what's already been stated, I would take a few pictures with and without the built-in flash, run through the menu for obvious signs of issues. remove the lens and inspect the mirror for scratches, remount the lens and then run the lens through the entire focal range for smooth operation. If you have a laptop, bring it along and download the images so that you can view them on the monitor. Check their sharpness, resolution and detail.
I would also definitely check the shutter actuations which can be found by using the steps found in this technical paper at Biofos.com