From the Google Webmaster Central Blog:

While maintaining a website, webmasters may decide to move the whole website or parts of it to a new location. For example, you might move content from a subdirectory to a subdomain, or to a completely new domain. Changing the location of your content can involve a bit of effort, but it’s worth doing it properly.

To help search engines understand your new site structure better and make your site more user-friendly, make sure to follow these guidelines:

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From the Google Webmaster Central blog:

Google has said before that search engine optimization, or SEO, can be positive and constructive—and we’re not the only ones. Effective search engine optimization can make a site more crawlable and make individual pages more accessible and easier to find. Search engine optimization includes things as simple as keyword research to ensure that the right words are on the page, not just industry jargon that normal people will never type.
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