First make sure the gun fits you correctly and you have correct eyesight along the rib.
make sure the length from the trigger to the butt [lop]is correct.
check the stock and forearm for cracks,most can be repaired but may cost $$.
Check action and safety and make sure they work smoothly.
Be sure choke is the right one for the use that you will be putting it to this will be made a bit easier if you have a variable choke.
Hope this helps and enjoy your new[used] gun.
Charlie