One powerful way to refine your searches is by using search prefixes: words that you follow with a colon and then the search term itself. Search prefixes work with most  search engines.

For instance, use the prefix "site" to specify that you’d like to restrict your search to a particular site. The search phrase "site:microsoft.com windows xp downloads," for example, tells a search engine that you’d like it to retrieve links to downloads applicable to Windows XP from Microsoft’s web pages.

You can use the "filetype" prefix to search for specific types of documents or files. This is very useful if you’re searching for, say, Excel files–or for PDFs that you can download and print out in an attractive format. Let’s say, for example, that you’d like to search for a PDF of Ernest Hemingway’s novel The Sun Also Rises. The proper search phrase would be "sun also rises filetype:pdf."

Other handy prefixes include "define," for searching for definitions, and "related," to search for sites that are similar to ones you like. The "define" prefix is especially nice for students, young and old, who can instantly retrieve definitions of a word from a wide variety of sources.