Search within a Specific Site or Domain
Precede your query with site: if you know you want your answer from within a specific site or type of site (.org, .edu). For example: site:edu or site:nytimes.com.
Search by File Type
Search for specific types of files, such as PDFs, PPTs, or XLS, by adding filetype: and the 3-letter file abbreviation.
Include or Ignore Words and Characters in Your Search
Highlight common words and characters such as the and & if they are essential to your search (as in a movie or book title) by putting quotation marks "the" around them. You can also use the minus - sign to specify particular items you don't want in your results, like ingredients in a recipe.
Get results that include synonyms by placing the ~ sign immediately in front of your search term. A search for Christmas ~dessert recipes, for instance, will return results for desserts, along with candy, cookies and other treats.
Other Tips and Tricks
For more help see the Google Search Tips page