Whether someone's stolen your credentials or you really can't remember your password, if you're ever locked out of your Facebook account, there are a number of routes you can take to get back in. One of the most effective needs to be set up in advance: telling Facebook who you trust the most.
If you think about it, it's actually more secure than knowing your birthday or the name of your first pet or your middle name (all of which can be guessed or obtained through social hacking). Unless a would-be hacker has rounded up or bribed your closest friends as well as stealing your login details then your pals will be able to get you back up and running. Facebook calls it Trusted Contacts.
The idea is if you get locked out of your account, you can call a designated friend or family member. Facebook already knows you're linked to them on the social network, and knows you've specified them as trustworthy, and that gives them the authority to access special one-time codes that they than pass back to you to regain access.
From Facebook Settings on the web, click Security and then Edit next to the trusted contacts heading. You should pick people who are likely to be in the country and available, because you're going to need codes from all of them to regain access to a locked account. Facebook lets you pick three, four, or five contacts.
It's not a replacement for the other security measures Facebook has (which you should also switch on), but if you find yourself reaching a dead-end with other password recovery methods, it's a good backup to have.
For security reasons, your friends get a notification that you trust them, and you should probably explain it to them just in case. After all, you don't want them ignoring your call when you're battling to get your social media life back.