Facebook has a number of privacy settings, some of which are difficult to find. In the adjoining column, I've included several of the most important ones. Take a few moments to review the procedures and check your settings. Even if you think you have everything set as you'd like, you might be surprised.
Updated June 10, 2013
Did you know that apps can gather just about any information you post or share on Facebook? Whenever a friend uses an app, the app can access whatever information you designate. Yet I think most people are unaware that the settings exist. Be sure and review this procedure, and then check your settings.
It's possible to set how much information to share with those that are not friends: the general public. You can share everything, only the bare minimum, and everything in between.
I recommend that you review this procedure and check your own profile. Make sure you're only making available the information you're comfortable sharing. Also, it's good to check this periodically, as Facebook continually tweaks settings. Even when you think you have everything set, they'll change something.