Search engines such as Google have built their business models on selling keywords from user searches to advertisers, so searches are never private. Privacy advocates recommend you never ask Google or any other search engine anything you would not be comfortable sharing publicly—with your boss, lover or worst enemy. By self-censoring, you limit the information Google can sell advertisers.
Also, limit the amount of personal information you share online including birthdays, phone numbers and addresses. If your birthday is already on Facebook, make up a fake birthday and spread it around to make it harder for thieves to steal your identity. I also give my location as that of a nearby town, not the actual town where I live.
These and a lot more suggestions for maintaining your privacy may be found in an article by Harriet Taylor in Today Money at http://www.today.com/money/low-tech-ways-you-can-protect-your-privacy-online-t28161.