How to root Samsung Galaxy Duos GT-I9082
First you need to Download SuperUser file.
Copy this file (UPDATE-SuperSU-v1.25.zip) from your PC to SD card and disconnect your device from PC.
Now reboot your mobile in CWM recovery mode, So to do that press then hold Volume Up button + Home buttons + Power button together until Samsung logo blinks twice then release the Power key but you should keep the other two buttons at same condition until you will see blue texts and black background and Android bot appears.
Now you are in the recovery mode, you have to select to install zip from sdcard and then you should select choose the zip from SD card and then choose the Superuser file named as UPDATE-SuperSU-v1.25.zip and then select yes to start the process.
Now this process will take some time to finish, after the process is finished come back into the recovery mode and finally select reboot system now, tis will reboot your system.