This is the general or a universal method of resetting all Lumia phones when you have been shut out either by forgotten the password/ lock. This method is known to work for all Windows Lumia device.

Note:
resetting your lumia device will lead to lose in personal data such as apps, music, videos, pictures, and it also restores the default factory settings.

Steps involved in resetting a lumia phone

1. Ensure that your Lumia device is fully charged. If your phone isn’t well charged, kindly plug it on charger and wait for some minutes minutes. (Skip this step if phone is fully charged)

2. Turn/switch off your device, and make sure you disconnect the charger (if plugged in).

3. Press and hold the volume down key, and then connect/plug back the charger. An exclamation mark (!) will appear on the phone’s screen.

4. Now, press the buttons exactly in the as arranged: volume up, volume down, power, and volume down.

5. Phone will reset as soon as you do step four(4), a double gears icon will appear and it should be rotating on the screen for up to 5 minutes, after which the screen goes blank for 30 seconds and then your phone will restart.

6. Its done, next is to go through setting up process just like when you bought the phone newly.. Be very observant and ensure to enter values correctly. [Time and date, Microsoft account(can be skipped) and many others.]

7. Disconnect the charger and continue to enjoy your device.