Just like you should check your approved Facebook apps every once in a while, you should review all the installed apps on your phone. Get rid of any you don't use AND make sure the ones you do aren't spewing tons of data to advertisers (or worse) in the background.

Free Apps May Be Tracking Your Phone Without Your Consent
Free Android apps are getting a bit promiscuous. That, at least, is the conclusion of a group of security researchers, who find that poorly vetted apps on Google Play are connecting to a massive number of ad and tracking sites—without users being any the wiser.