Here’s one quick tip to earn “easy” links
Crawl Errors on Google Webmaster Tools
In Google Webmaster tools, look for “Diagnosis -> Crawl Errors”
It will show you the list of the pages that Google wasn’t able to crawl. Most of the cases it will show you a lot of 404 pages within your own site, or you can also find external links from external pages that are pointing to the wrong page.
In the same table, click on the column “Linked from” to discover which pages are linking to 404 pages.
After you identify some valuable links, place a permanent redirect to the ‘404’ page to the most adequate page of your site and gain some extra link juice to those pages.
You could be surprised at how many 404 pages are receiving some link juice. Just redirect those to the appropriate pages and you’ll get some ‘free links’ 
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