How Webmasters can proactively address duplicate content issues

[mandy]

How can Webmasters proactively address duplicate content issues?

    * Block appropriately: Rather than letting our algorithms determine the "best" version of a document, you may wish to help guide us to your preferred version. For instance, if you don't want us to index the printer versions of your site's articles, disallow those directories or make use of regular expressions in your robots.txt file.
    * Use 301s: If you have restructured your site, use 301 redirects ("RedirectPermanent") in your .htaccess file to smartly redirect users, the Googlebot, and other spiders.
    * Be consistent: Endeavor to keep your internal linking consistent; don't link to /page/ and /page and /page/index.htm.
    * Use TLDs: To help us serve the most appropriate version of a document, use top level domains whenever possible to handle country-specific content. We're more likely to know that .de indicates Germany-focused content, for instance, than /de or de.example.com.
    * Syndicate carefully: If you syndicate your content on other sites, make sure they include a link back to the original article on each syndicated article. Even with that, note that we'll always show the (unblocked) version we think is most appropriate for users in each given search, which may or may not be the version you'd prefer.
    * Use the preferred domain feature of webmaster tools: If other sites link to yours using both the www and non-www version of your URLs, you can let us know which way you prefer your site to be indexed.
    * Minimize boilerplate repetition: For instance, instead of including lengthy copyright text on the bottom of every page, include a very brief summary and then link to a page with more details.
    * Avoid publishing stubs: Users don't like seeing "empty" pages, so avoid placeholders where possible. This means not publishing (or at least blocking) pages with zero reviews, no real estate listings, etc., so users (and bots) aren't subjected to a zillion instances of "Below you'll find a superb list of all the great rental opportunities in [insert cityname]..." with no actual listings.
    * Understand your CMS: Make sure you're familiar with how content is displayed on your Web site, particularly if it includes a blog, a forum, or related system that often shows the same content in multiple formats...   

full article: http://googlewebmastercentral.blogspot.c...ntent.html