Google does a nice job of giving you access to the data it has gathered about you and that you have connected to your Gmail or Google Apps account.
There is a wealth of information here, including all of the personal information that is connected to your account. Here you can change your display name, contact information, profile picture and more.
In the "security" tab you can change your password and view account permissions. I highly recommend that you take a few minutes to go through the "secure your account" section which will:
- Display your account recovery email address and phone number.
- Display your login activity by location to ensure that only you are accessing your account.
- Display apps and devices that are connected to your account. It is a good idea to remove any devices or services you are no longer using.
Once you have completed this security audit, I recommend that you click on the "data tools" tab and select "view account data". This page displays all of the data associated with your Google account by product. You can see how many emails you've sent, appointments are on your calendar, etc. Sign up for a monthly summary of this data by clicking the check box at the top of the screen. Each monthly, quickly review the email to ensure that no unauthorized devices or services are accessing your account and that there is no suspicious activity going on.
The final step is to periodically (monthly) create a backup of your Google account data. Just find the "download your data" box and create a new archive (note: this is the Google Takeout service). You can leave it on the web, or download a copy to your computer (it may be large depending on how much you use your Google Account! My backup was 20gb!)
Once you know the data, devices, and services that are connected to your account, you can monitor, clean up, and manage that data to minimize the risk of unwanted intrusion or misuse of your information.