Source: http://blog.raventools.com/resolve-duplicate-content-issues/
You might be one of many website owners who find it hard to manage duplicate content. Here are 10 scenarios with solutions that can help you manage it.
Fixing duplicate content issues
1. You have many eCommerce product pages.
How To Solve This: Use rel=canonical on your product’s page URL and point them to the proper category. This will tell google which is your preferred URL.
2. When you republished someone else’s content on your website.
How To Solve This: Using SEO Yoast Plugin, it would be easy to assign it’s source content using rel=canonical.
3. You have printer-friendly website.
How To Solve This: In the robots meta tag, Add noindex, follow, noarchive and add the canonical URL.
4. When you have to republish corporate news that is already published on the company’s website.
How To Solve This: Create a unique version of the news item by combining content from multiple sources.
5. When you have an older CMS and it’s got identical meta data on your pages.
How To Solve This: Switch to another CMS that allows you edit metadata such as page titles and meta descriptions ASAP.
6. Switching your site from HTTP to HTTPs resulting in 2 versions of the same site.
How To Solve This: When switching to HTTPs, make sure you do it right the first time.
7. When your domain name does not resolve to one dedicated domain name, eg. http:// does not resolve to http://www
How To Solve This: Use 301 to redirect the http:// to http://www or vice versa.
8. When your content is being stolen by websites with spammy content.
How To Solve This: Check on bots or unauthorized scrapers on Google Webmaster Tool. Most of the time scrapers are bots and you can slow them down through your .htaccess file. If it doesn’t work, file a report directly to google using the Scraper Report Form.
9. People are stealing your traffic by inserting your content on their site using iframes
How To Solve This: Find the site’s host company and the domain registrant’s email using whois tools and contact them to remove your content. If it doesn’t work email them a DMCA takedown notice.
10. You have a fairly large website and your internal links are unmanageable.
How To Solve This: Use rel=canonical on duplicate pages and restructure your site’s navigation.