Check which system services are using your location
Under the list of apps in Location Services there is a second list, with a dozen switches nobody has ever opened.
Tips tagged #privacy
Stop strangers AirDropping things to your Mac
Set to Everyone, AirDrop lets anyone in the same carriage put a picture on your screen.
Stop your Mac reporting back to Apple
Usage analytics, data for developers, your searches and ad personalisation each have a switch, spread across three panels.
Encrypt the startup disk with FileVault
Your disk is already encrypted; without FileVault the Mac can unlock it on its own, with no password from you.