(1) Launch a test site and restrict everything in robots.txt.
(2) If any page name is different, 301 redirect them in .htaccess.
(3) Test, test, test it.
(4) Transfer from old to new website.
(5) Submit a sitemap with new page links to Google.

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Advertising without research is like shooting an arrow into the air and
then looking up for a target to catch it with.