How do you unblock somebody on Facebook?

First Go up to the corner where it says "Home" then next to that should me an arrow then go on "Privacy Settings" then scroll down to the bottom where it says " Blocked People and Apps". Then go to " Manage Blocking" then click on the person you want to unblock.

P.S This works great & might come in handy i blocked one of my friends by accident so hope this information goes in use one day. bye :)