Some easy steps to follow :-
- Remove battery or complete power off your device.
- If battery remove please insert again and press volume up+home+power key at the same time.
- When Samsung logo show on screen then release power key but press volume up and home key.
- Release both key when recovery menu appears on the screen.
- Select wipe data/factory reset with power key.
- Select Yes — delete all user data wait for complete when complete press power key to reboot.
Note:-Most of Samsung mobile phone can be hard reset with combination of volume up+home+power key.