Facebook, since its mistakes with the Beacon advertising incident, has rolled out one of the most robust security systems for any social network, which allows users to control who sees what information about them with great specificity. Take a look at Facebook's privacy features and how to set yours.
Privacy Main Menu
Now you're at the main privacy overview. It consists of four privacy controls: Profile, Search, News Feed and Wall, and Applications. Click on "Profile." It's a good place to start since it's your publicly facing site on Facebook. Start with the "Basic" tab.