Recently hackcollege.com post info-graphic on how to search on Google.It will improve the way you search on Google.It will help you to find the particular file on Google for an example if you want to find the PDF file .You have to search like "filetype:pdf keyword" this query will find a PDF file containing your keyword.So take a look at that info-graphic below. I hope you understand well next time you will search something on Google you keep in mind all these things.It will definitely improve the way you search on Google.