Google.com > Advanced Search
Note: Google is always trying to improve by applying artificial intelligence to interpret what you are looking for, so rules may change over time.

Useful commands in the search string:
Notation - search command is enclosed in [ ] below.
Commands:
  OR - Conditional results (you can use "|" in place of OR)
  AND - Is always the default so is not necerssary
  [-word]  - Exclude results with word e.g. [newark -deleware]
  "NBA playoffs"   exact phrase
  "Goerge * Bush"  Wild Card - 1 string (word or initial) (use * * for two words)
     (Does not match null. i.e. will not find "George Bush")
  ~ Synonyms:  ~reviews = reviews, review, reviewer, guide, rating, prices,
                         opinions, comparisons
      ~vintage = old, antique, ...  (good for photos)
    [2000..2009]  2000, 2001, ... 2009
   site:nytimes.com
   

Case doesn't matter "CA" is the same as "ca"
   
   
Search most recent:
   Click on "Search Tools" in search results page
   Then on "Any Time" to get time choices.
   
   or go to www.google.com/advanced_search
   
   or edit the address in the location barThe syntax of the string to add to the end of the URL is &tbs=qdr:
   plus d, w, m or y for day, week, month or year.  Thus:
     &tbs=qdr:h [past hour]
     &tbs=qdr:d [past 24 hours (day)]
     &tbs=qdr:w [past week]
     &tbs=qdr:m [past month]
     &tbs=qdr:y [past year]
     or

 Get the date a page was modified:
     Insert the code javascript:alert(document.lastModified) in the address bar.
     (Does not work with safari)
     Download the Link Diagnosis Firefox extension from LinkDiagnosis.
     Right-click on the webpage
     
 Searching with latitude and longitude coordinates:
 37.771008, -122.41175
 +37\0xFFFD 14.596', -118\0xFFFD 43.611'

   
 Other Tips:
   Note: Google keeps refining their search engine.  Some of the numbers below have changed.
   Word sequence matters:
      [duck blind] gives 1.2M hits with "duck blind" high on the list
      [blind duck] gives 500K hits
   Automatic synonyns:
    Search usually includes plurals of words e.g. "phone" also finds "phones"
    However, tense does matter: search the web produces 80 M hits
                                searching the web produces 3 M hits
                                
    Words for numbers are not the same:
              fifty states also finds "50 states" and 31 M hits
              50 states does not find "fifty states" and gets 9 M hits
    
    ["fisherman's wharf" "san Francisco" California] finds "san francisco, ca" also
     However,
       ["fisherman's wharf"  San Francisco, CA] gives 8M hits
       ["fisherman's wharf" "san Francisco" California] gives 8M hits
       ["fisherman's wharf" "san Francisco" California OR CA] gives 10M hits
       I don't know why

• If you get a "Page Not Found (040 error)" or the page you get doesn't have the item you searched for.
  Go back and look for "Cached" at the end of the item in the search result.
  Click it to go the the old copy of the page that was indexed.
• If a page is very close to what you want, go back and click on "Similar Pages" in the search result to get other pages like it.

Unique Google Search Operators You May Not Have Seen | PetesBloggerama
Joel May's tips:
  Everything Google
  20 Tips for More Efficient Google Searches
  Advanced Search Operators
Google cheatsheet | dmcritchie.mvps.org
Search Operators at www.googleguide.com/advanced_operators.html
Search Engine Optimization (SEO)
Tips for Searching Effectively with Google at about.com