Regarding Google services: When you enable Two-Factor Authentication, they give you the option of printing a "one time pad" with six codes on it. You then pri

Regarding Google services: When you enable Two-Factor Authentication, they give you the option of printing a "one time pad" with six codes on it. You then print this out and keep it safe somewhere. That way you can get into your account even if your phone and other contact points are compromised. This won't do you any good if someone has deleted your google accounts or reset the 2FA system, but for more "normal" scenarios it can be a life-saver.