Google Tell: How to deftly deal with duplicate content

Google became more care about the duplicate content on its search result, for give user better search experience, they gave some advices to webmasters. These suggestions is good for help webmaster to keep SERP on Google.com.

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. (I don't think so, like print page is very helpful，will not delete it.)
* 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. (no need to do it. update your sitemap should be OK)
* Be consistent: Endeavor to keep your internal linking consistent; don't link to /page/ and /page and /page/index.htm. (It's hard to do, especially for huge site.)
* 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. (good idea)
* 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. (if some guy steal your web page and don't link back to you, that would be harmful to you? )
* 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. (how about to access with IP addess?)
* 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. (How big it is? what's the suggested limitation? under 1024bytes?)
* 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. (good idea)
* 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. (sometimes it's rational to show the same content in different ways, cause different people have different habits)
* Don't worry be happy: Don't fret too much about sites that scrape (misappropriate and republish) your content. Though annoying, it's highly unlikely that such sites can negatively impact your site's presence in Google. If you do spot a case that's particularly frustrating, you are welcome to file a DMCA request to claim ownership of the content and have us deal with the rogue site. (good idea)