I know what you're thinking--but hear me out. Plenty of reasons for doing an online background check exist, and not all of them are sketchy.
In fact, everyone should do at least one online background check on--you guessed it--themselves. After all, if you can find out sensitive information about yourself with a little (free) online sleuthing, there's no telling what employers, stalkers, and ex-girlfriends or -boyfriends will be able to uncover.
So here's how to do a thorough online background check without dropping any cash.
If You Know Your Target's Name
If you know name of the person you're looking for, the first places you should check are the usual venues--good old search engines and social networks. Google, Facebook, LinkedIn, and Twitter are all good stepping-stones for discovering valuable information about people.
Remember to use advanced search techniques when looking people up on Google or other search engines. Just enclosing your search terms in quotation marks will help immensely in weeding out noncorrelated or irrelevant search results. If the person you're searching for has a common name, you should also add any information you know about them after the quotation marks. For example, if I search for "sarah jacobsson purewal" pcworld, I'm going to get more details about the Sarah Jacobsson Purewal who writes for PCWorld, helping to narrow my search down a bit.
Use any information you know about this person, including places of work, types of work, schools they've attended, cities they've lived in, and the names of other people they know. You can also use site-specific searches if you're looking for someone within a school or business. For example: site:pcworld.com "sarah jacobsson purewal" will give a list of search results found only in the PCWorld.com domain.
Searching Your Social Networks
Social networks are fantastic sources of information--and it's all completely self-volunteered. This is why social networks are particularly handy for employers--because if it's on your Facebook page, it's not only information about you, it's information you've chosen to share with the world.
Facebook is indisputably the social networking standby--no surprise, as it boasts 500 million users. You can search for people by name and e-mail address, and modify the results by location, school, and workplace. If nothing shows up, they may have made their profile private and unsearchable.
If that's the case, you can do a site-specific Google search, and any public pages or groups they may have commented on will show up. For example, my personal Facebook profile is private and will not show up in Facebook search results, but if you type site:Facebook.com "Sarah Purewal" into Google, you'll see that I have commented on PCWorld's Facebook page. You can now see my profile picture, as Facebook doesn't allow users to make this private, even if you still can't search for me using Facebook's search.
Alternatively, you can use Openbook.org to search across Facebook's public pages (including status updates) for any search string you want and find search results listed with names, profile links, and pictures--perfect for your background check.
Other social networking sites, such as LinkedIn and Twitter, are also worth a look. LinkedIn usually reveals much less information about a user, because it's primarily a work-oriented social network. However, it is an excellent place to verify user's résumés and work histories (though, of course, a user can lie on his or her LinkedIn profile very easily).
Twitter is a different type of social network. Unlike Facebook and LinkedIn, Twitter asks for very little identifying information from their users. Thus, you'll often find people's Twitter accounts via their Facebook or LinkedIn pages--not necessarily by searching Twitter. Twitter can still give you a wealth of information, though it's more likely to give you an insight into their personality, interests, and style, rather than information you can use to find their address or phone number.
Find the Basics: Phone Number and Address
Okay, so you've Googled your target and discovered all of their sordid beer-bong photos on Facebook, but what you really want is to be able to contact them. How can you get their phone number and address?
ZabaSearch is a fairly accurate phone number lookup service. It offers a free way to look up people's phone numbers (you can narrow it down by state), along with premium services for reverse phone number and social security number lookups. I say "fairly accurate" because while ZabaSearch's database includes listed and unlisted numbers, it's hit-or-miss when it comes to cell phone numbers--and who doesn't have a cell phone these days?
WhitePages.com also offers a free phone number lookup, and throws in an address to boot. WhitePages appears to update its database more frequently, as it found a recent address change of mine that ZabaSearch missed (within the last year). However, it does not list unlisted numbers. WhitePages also offers a premium, reverse phone number lookup, and will show you the location of the phone. Of course, this is simply the location of the phone's origin, and is based on the phone's area code--when I look up my phone number, for example, it says my phone is likely located in Conway, South Carolina. (This is incorrect, as my phone is currently located in California, but my phone's area code is from South Carolina.)
Criminal and Public Records
Finding an address or phone number is child's play. Only when you're looking for criminal and public records do things start to get interesting. If you want to know if your hot coworker has ever been divorced, or if your neighbor might be running a drug ring out of her apartment, this is how you can find out.
CriminalSearches allows you to do a criminal history check on people by name. You can also narrow down the search by city and state, though these are not required fields. The search results include the offender's birth date, address, and what types of criminal offenses they have committed (behavioral, business, drug/alcohol, sex-related, theft/robbery, violent, or traffic/other). It does cost money to see the details, and you should remember that some states include minor traffic citations as offenses--so they may not really be "criminals," per se.
If you're looking for other types of public records--such as marriage records, birth records, or death records--SearchSystems offers access to free public records sites. You can search by type of record, zip code, state, county and state, or city and state, or you can search international records by region. Instead of "searching," however, you will end up being directed to the Website that contains the records you're looking for--whether it's Clinton County Cemeteries or California marriage licenses before 1900.
VirtualGumshoe also has a database of public records Websites, including wanted lists, marriage and divorce records, voter records, and death records. Some of these sites are free, while others are pay services, but little icons by each listing will let you know which is which.