via pcworld.com...
If you use Gmail, Google Docs, or any other popular G-service, you’re about to surrender a lot more personal information to the Googleplex...unless you take these steps to prevent it. 
1. Check the Dashboard Your first destination is Google Dashboard. It provides an overview of the information Google has stored on your account across many of its most popular services. To get started, go to google.com/dashboard and log in with your Google account (typically an email address). There, you can see much of the data that Google has on you--from your Google+ account to your Gmail account.
Take a few minutes to click through the various services and to review the information Google is storing. Then clear out any data you no longer want associated with your account.
2. Clear Your Google Web History
3. Tweak Your Ads Preferences
4. Liberate Your Data
If you want to remove some (but not all) of your personal data from multiple Google services, head over to Google Takeout, which lets you download a copy of your data from Google Buzz, Circles, Docs, Picasa Web Albums, Gmail contacts, and other tools and services. Get started by logging in to the Google Takeout page.
5. The Nuclear Option: Delete Your Google Account
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