In the past, the only way to get better results were to register for personalized search. Now you can get personalized results each time you use Google. Depending on whether or not you're logged into a Google account when searching, the information used to personalize your experience will be different:
Signed in customization: When you're logged in, Google personalized search experience based on your web history. If you do not wish to receive customized results while connected, you can disable and delete Web History from your Google account. You can also view and remove individual items from your web history.
Signed out of customization: When you're not registered, Google personalized search experience based on past research information linked to your browser, using a cookie. Google stores up to 180 days of search activity linked to output signed cookies in your browser, including queries and results are clicked.
Because many people might find on a single computer, the browser cookie may be associated with search activity more than one person. For this reason, do not provide a way to see this activity log signed out. If you do not wish to receive customized results while disconnected, you can disable these custom search.