Hi Waseem312
First of all it would be good to buy the card only if you have some sort of warranty even if it's a month or so to test it properly.
Phisically you need to inspect if the fans spinning easily without any noise also if theres no phisical damage to the components on PCB. The second thing is to run a benchmark ( like 3D Mark ) to see how it behaves during strees and monitor temperatures ( software like CPUID ).