Some useful commands are listed below:
1.If you want to find a pdf file or a book you can simply go to google and search using : filetype:pdf and search. For example you are looking for a book name twilight so go to google and type the following codes : twilight filetype:pdf
2.If you are looking to find the meaning of any specific word then first type define and then enter your word. Example : define circumference
3.If you like to know weather of an specific area then you can simply type weather and then the area name. Example : weather london.
4.You can also use google as a calculator. For example you like to find how much will be 100-40+50-2+63+242-233 then you will find the answer will be 180.
5. If you are looking for any currency of any country you can also do it using google. For example you would like to find how much is 1 dollar in pounds. So just search in google : dollar to pound. For example : dollar to euro , dollar to pound.
6.if you would like to find all pages related to any perticular website then just type link: and then the website name. Example : link:http://www.tipsglobe.com
7. If you are looking for a mp3 in file sharing website like mediafire , 4shared , rapidshare and others then first enter the host name like mediafire: then give the name of your mp3 file. Example : mediafire: its my life.mp3.
8. If you are looking for a movie and want to search it using google you can use the simple commands : -inurl:htm -inurl:html -inurl:php intitle:”index of? (mpg|avi|wmv) "The Elite".The (mpg|avi|wmv) operator can also be written (mpg or avi or wmv).