These days Google has published a few specific ways to optimize web sites for search engines in the case of "move" of the site.
By "movement" Google understands changing the URL of the website, and/or changing underlying infrastructure serving the website without any visible changes to the URL structure.
According to Google, such a change can have disastrous effects on the visibility of the website unless conforming the SEO rules.
The new Google guide is divided into four chapters:
What is a site move?
Move your site
Use the change of address tool
Withdraw a change of address
The guide includes information about how to set the new hosting infrastructure, mapping URLs, and traffic monitoring. All changes must be reported to Google Webmaster Tools account for a fast and accurate update of data from the database of the search engine.