Hello, I am planning to move from my current host to another one. I want to avoid down time but also loosing Google PR and SERP. I am planning to first copy the site on the new host, while leaving a copy of the site on the still active old host. Then, update the registrar pointing to the new host. However, I have to wait 72H until routing table are updated. During that period, do I face google bot finding twice the same content and tag my site as duplicate content? Should I add a redirect in the .htaccess to the new host? How should I do this? Thanks for the assistance.
That is exactly how Google recommends you transfer a website.. Routing tables are updated at various speeds.. Once the one Google uses is updated it will not see the 'old' site so there is no duplicate content issue..
Once your updated site is indexed by Google you can remove the content from your old site to avoid duplication penalty. Changing to a new host won't be a problem.