Google supports several operators which gives you more control on search results. There are too many search operators to remember. Also, not all of them are useful all the time.
So I am describing today only the most frequently used search operators alongwith real-life examples. College students will particularly find examples more interesting! 
>> First note common syntax of following Google search operators…
operator:parameter
There should not be any space on either side of colon [:]
Also all search operator are case-sensitive!
# site: This operator is useful for searching a site and/or its subdomain.
- site:devilsworkshop.org will restrict search to all subdomain under devilsworkshop.org
- site:edu will search all site in edu top domain. Useful for researchers and college students while studying and writing for papers as site:edu will restrict search results to the educational sites!
# filetype: You can directly use Google to search any type of files.
- filetype:ppt to search all presentation slides. This is how I manage to create presentations just one night before!
- filetype:pdf will search only pdf files! Good for searching ebooks.
- filetype:pdf site:edu will return all files with pdf extensions from edu domain. Useful to complete journals or study assignments!
# inurl: To search something in URLs
- inurl:md5 will find keyword md5 in URLs.
- inurl:md5 filetype:java will return all java source files with md5 in their name or URL. How about using this to complete programming assignments in college!
Also try allinurl: operator which looks all keywords into URL only!
# intitle: To search something in page title. Useful when searching a too common word.
- intitle:md5 will return all documents having md5 in their title.
- intitle:Hacking filetype:pdf will return all pdf files i.e. mostly ebooks and papers about hacking.
Also try allintitle: operator which looks all keywords into title only!
# define: To use Google search as dictionary. There are other dedicated dictionary services but none of them is as clean and fast as Google.
- define:hacker will show meanings of hacker.
- define:network security will return meaning of network security.
- Note: Do not type anything before define: or combine it with other operators!
# OR - To combine results of multiple searches! By default Google performs ANDing on keywords we use while searching. But sometimes explicit OR can help more.
- filetype:pdf OR filetype:doc will search for pdf as well as doc files. This will help you complete your journals
- site:en.wikipedia.org OR site:howstuffworks.com will restrict search to Wikipedia English and How Stuff Works site!
Note OR must be in capital and it doesn’t have colon after it!
In case you are interested in complete list, its here… (printable format)
Related Google Trick: Live Cricket Scores – Just One-Click Away!
[Updates: A small typo fix by Vinzz]
[...] Also check 6 Most Frequently Used Google Search Operators For Better Searching! [...]
I have been using a few of these tricks before. Especially the filetype:torrent is quite a good way to search for torrents! The intitle and inurl commands are NEW to me! Thanx for the info!
@Praveen
Also make use of “define:”
The result it gives are really much better from searching dictionary.com
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Hi Rahul, any reason behind naming this WebSite like this.. jus to know:)
i mean as “Devil’s Workshop”
Google search is a web search engine owned by Google Inc. and is the most-used search engine on the Web.[3] Google receives several hundred million queries each day through its various services
fileype:ppt is my favourite operator use it always even set up a search engine to search powerpoint presentations using it