Encrypt your handset
Encrypting the handset provides that extra bit of security for your files and means that if your device is lost or stolen, it won't boot without your passcode.
It takes around an hour to complete the encryption process - and can be done by going to Settings > Encryption. Everytime you turn on the device it will ask you to enter a pin/password before booting up. The lockscreen will also be secured with the same password combination.