go to http://google.security.com
Threatpost has a good post of the Security devices and Activities link https://www.google.com/settings/security
The most important part is reviewing your Google activity periodically and to reduce any app permissions if you no longer use them.
Also for administrators the secureaccount link: https://security.google.com/settings/security/secureaccount
The review of online activity is a good aspect of online identity vigilance.