Google can provide plenty of useful information during footprinting process. Google hacking have been around for a long time although it is not widely known to the public. The process is simple but effective. We will use fine-tuned operators to get precise information.
Using Google hacking we can get information on

File types
Logon Portals
Configuration Data



Lets look at the operators that make this possible. Each operator is entered directly in the google search window.

1. cache
Displayes the version of a web page that Google contains in the cache and not the current version.

2. link
Shows websites with links to the specified site. In our case

3. info
Shows information about listed page

4. site
Restricts searches to location specified. In our case we search for myword
Example: myword

4. allintitle
Returns pages with specific keywords in there title
Example: allintitle:keywords

4. allinurl
Restricts searches to url with keywords specified
Example: allinnurl:keywords

5. related
Find sites that are similar to a web address you already know.

6. OR
Find pages that might use one of several words.
Example: marathon OR race

Here is very good source for reference:
Also be careful and don’t do too many queries at ones as google can shut them down.