Google has numerous specialized search features.  A good one for people searches is a domain specific search.  By adding site:anysiteaddress.com to your search string, you can narrow your results to a given domain.  You can even widen your search to specific top-level domains like .com, .gov, . edu, .mil etc. 

For instance, students, alumni, faculty and staff for major universities will often be mentioned, along with contact information, on  university web sites.  Say you know the name of a student, alumni or staff member at Berkeley, you could do a person search like John Doe site:berkeley.edu or a more specific string search like "John Doe" site:berkeley.edu [ make sure to include a space between your last search term and site:anysiteaddress.com ].

Say you want to find a current or former member or civilian employee of the US military and you want to see if they are mentioned on any of the military sites - you could do a search like John Doe site:navy.mil, if you know the person is affiliated with the US Navy.  You could also do a general top-level domain people search like John Doe site:mil, if you are unsure of the branch the person belongs too and want to search all of the .mil sites.

The same people search techniques work for private business [ .com ] or non profit [ .org ] employees.  Try a Google people search like Bill Gates site:microsoft.com and you get the idea of how you can use this to find less public figures.  In addition, don’t forget the basics of people searching - there is a difference between a general people search for Bill Gates and a specific, exact string search like "Bill Gates".

Here is a great primer for anyone interested in starting their own people searches.  Whether you are trying to find family or working on a genealogy search; trying to find classmates or former coworkers; looking for former military buddies or trying to locate people for judgements or other monies owed to you, these Skip Tracing 101 tips are a great introduction to doing it yourself, without the expense of hiring a professional.

Most professional investigators and skip tracers will already be familiar with the people search tools presented in these tips, but the articles are great for the amateur people searcher.  Skip tracing 101 has three parts:

Skip Tracing 101 - Part I
Skip Tracing 101 - Part II
Skip Tracing 101 - Part III

You can also find the internet’s top free people searches, reverse searches and public records sites at 411×411.com Free People Search Directory

Are you searching for a family member; former classmates; past friends or coworkers?  If so, then you may want to start your people search by posting a message to the Craigslist community message boards.  The craigslist boards have a Missed Connections section under the Personals area, where you can post messages about people you are searching for.   

The type and amount of information that you choose to include in your people search post is up to you, but be sure to post it in the city where the person is likely to be found.  For instance, if the person you are searching for has ties to San Francisco and you live in NYC, then post the people search message in the San Francisco Missed Connections section. 

You can find a list of available cities at Craigslist .  Choose your city, then choose Missed Connections under the Personals section.  You will need a valid email address to make a people search post on these boards.

There are currently over one billion messages posted and archived on Google Groups.  People will very often use all or part of their real names when posting messages in these forums.   This provides a great  opportunity for people searches.

I recently found posts on these forums from a past college friend by doing some simple searches.  You can do a general search for an individual like John Doe, which will search for any mention of the person in any of the messages.  To weed down larger results you may want to try "John Doe" in quotation marks to find an exact string match or a search for just Doe or J. Doe for more general searching.

In addition, you can search specifically for authors of posts. For instance, author:John Doe or author:J. Doe or even author:Doe will search for posts where these names appear as an author of the message. Make sure there are no spaces between the colon after author and the beginning of the name you are searching for.  Spaces should be left between first and last names in the people search.

You can try your own people searches here at  Google Groups.

The first three digits of a valid social security number are considered the area number.  If you know these first three SSN digits for someone you are searching for, it can help in locating a previous state of residence and possibly family members. 

For instance, say someone you are looking for has the social security area number of 305 and a fairly uncommon last name.  By doing a social security area search, you will find out that the person’s SSN ( if valid ) was likely issued in the state of Indiana and more than likely that person has lived in this state at one point or another.  Now a whitepages last name only search for the state of Indiana may turn up one or more possible relatives with the same last name residing in Indiana, who may know of the person’s whereabouts. 

You can do social security area number searches at 411 x 411 SSN Area Number Search . Whitepages and other people searches can be done at 411 x 411 Free People Searches