Search engines are designed with the average user in mind. For most people most of the time, that is great. When we are conducting in-depth research, however, that behind-the-scenes customization winds up giving us relevance rankings that don't work. Even if you are not specifically logged in to a search engine, information on your search patterns, the links you click through, your location and other factors will alter what your search results look like. Even information such as what plug-ins you are using (which might indicate your level of techno-savvy) and your system fonts (which might suggest what language you write in) can result in search results being tweeked to your presumed interests. If you are looking for results that are as neutral as possible, this customization is a bug, not a feature.
Of course, there are times when this backend customization is helpful. If I needed in-depth information on a company, person or issue, I may get better results by using local versions of search engines. When I was looking for background on a Canadian company, for example, I started with the Canadian versions of Google and Bing.
But what about those times when you really want to cast as broad a net as possible, and you don't want a search engine to try to anticipate what you are looking for? One approach is to use a search engine's private search mode, in which no browser or search history is kept, nor are cookies saved. Chrome, for example, offers Incognito mode, which you open by clicking the wrench icon in the upper right corner. Internet Explorer lets you select "InPrivate Browsing" by clicking Tools, then InPrivate Browsing. Firefox has Private Browsing, which you start by clicking Tools, then Start Private Browsing. And, of course, any browser will allow you to clear your searching and browsing history, cookies, cache and related information.
While these are useful in keeping information from being saved after your search, the bigger problem is that search engines use the information that our browsers "leak" to customize search results. Even private-mode searching will reveal your IP address, time zone, plug-ins and installed fonts, all of which can alter search results. (Want to see what your browser is telling web sites? Use Panopticlick to find out.) Fortunately, we have some choices for further anonymizing our searching.
Scroogle.org offers completely anonymized Google searching (at the main page, click Scroogle Scraper to get started). Type in your query and Scroogle strips all identifiable information from the query, randomly grabs an IP address, and sends the query to Google. Google sends back a results page, along with a unique identifier cookie that is stripped away by Scroogle before delivering the page to you. This means that every search query Google gets from you is "fresh" -- that is, Google has no knowledge of your settings or prior searches, so you get virtually no unwanted personalization of the results.
Another search engine anonymizer is DuckDuckGo, which promotes the fact that it does not track your search history, send browser cookies, or transmit your search terms when you click a link on the search results page. DuckDuckGo relies on its own web crawler as well as results from Bing, Blekko, Yahoo! BOSS, and a number of other specialized sources.
And finally, there is Ixquick, a metasearch engine with some interesting features for in-depth searches. For example, if a URL appears in the search results of multiple search tools, Ixquicks adds from one to five stars to that link in the search results page, giving you more clues as to how useful each site may be. In addition, Ixquick does not store or pass on IP addresses or cookies, ensuring that you have a relatively private search. A sister site to Ixquick.com is StartPage, which is being marketed to British and American searchers. Curiously, unlike Ixquick, StartPage does not include the relevance stars in the search results. Also curiously, StartPage includes Google search results, something Ixquick does not.
There are, of course, many other anonymizer tools that let you browse the web anonymously. The resources described above are great for getting relatively un-personalized search results; for more security, look into a proxy server. Interestingly, Ixquick and StartPage include an option in each search results page to connect to any link on the page through the Ixquick proxy server, enabling you to view that web site without disclosing any of your information -- a nice touch when you want a bit more anonymity.