"This pocket guide provides precautionary and protective measures designed to mitigate the risk of using social networking sites. [...]  Limit outward signs of military affiliation (such as vehicle stickers, home decorations, using your rank in your address, or using military slang in public). Uniformed military members present in public venues or attending publicly accessible events should exercise vigilance.  Be unpredictable with smart behavior, routines, and travel.  Be alert. Maintain good situational awareness by staying alert, knowing what to look for, and knowing what is wrong or out of place.  Report all incidents of suspicious activity or behavior to appropriate authorities.  Think before you post. Always assume everyone in the world will be able to see what you are posting, or tweeting, even if the site limits your posts to your friends and family.  Do not allow others to tag you in images they post. Doing so makes you easier to locate and makes it easier to accurately reconstruct your network of friends, relatives, and associates."
Government Publishing Office: http://www.gpo.gov/