These are the steps to do a factory reset:
- Remove the battery and put it back in
- Hold down the ‘volume up’ + ‘volume down’ + ‘power button’ at the same time
- In the menu select ‘Recovery mode’
- When you see an Android with an exclamation mark, hold down the ‘volume up’ + ‘power button’ at the same time
- In the menu select ‘wipe data/factory reset’
- Confirm by selecting ‘Yes’
The system will now completely erase your phone. So also the contents of the SD card will be erased.
After this select the reboot option and you can start setting up your phone.
After connecting to your (WiFi) network and logging in with your Google account the phone will start downloading all the Apps you had installed. Apps installed by using a .apk will not be installed automatically, so you will have to install them manually.
Tip: Setup your phone to automatically upload your photos and videos by using Apps like Google+ or DropBox