If you use Nokia Touch Phone you can done following above picture by pressing Call Button/Camera Button/ Volume Button and Power button.
But if you use keypad mobile follow below steps:
1. Switch off your mobile.
2. Press and hold Star Button " * ", then "Call/Green" Button and also press "3" button on your phone.
3. Now power on your set.
4. Until the set completely start do not release all (*/green/3) buttons.
5. This is OK. Your phone will successfully restore without lock code.
(Important: Your all data will lost. So be careful, if need backup your important data)