Here is the official Google advice, followed by the ideas of others
via WebmasterWorld (the best place to discuss technical search engine
Change the URL of your website
Since Google's crawler associates the content of a page with its URL,
there is no way to manually change the URL that is displayed for your
website. The URL will be updated the next time we crawl your site. The
crawler revisits each site according to an automatic schedule, and we
cannot manually accelerate the date on which your site will be
If the URL of your website has changed since we last crawled it, you
may use the URL submission form and the URL removal methods described
below. However, the URL submission form does not take effect
immediately, so using the URL removal feature may leave your website
inaccessible from Google until we crawl your site again.
Instead of requesting a change from Google, we recommend that you ask
the sites currently linked to your old site to update their links (to
point to your new site). Also, don't forget to change any entries you
may have in the Yahoo! directory and the Open Directory. Finally, if
your old URLs redirect to your new site using HTTP 301 (permanent)
redirects, our crawler will know to use the new URL. Changes made in
this way will take 6-8 weeks to be reflected in Google.
"I recently moved a site without any problems vis-a-vis Google. This
was both a server move and a domain name change; I moved from a "free"
web-hosting domain to a "real" .org domain with a lot more space,
features and controls for security.
After registering the new domain name and waiting for it to propagate,
I copied the content to the new server, got most of my incoming links
switched over to cite the new domain URLs, and got my DMOZ and other
directory listings updated. I then put a 301 (permanent) redirect on
the old server to point each old URL over to the new one, and finally
removed almost all of the content from the old server. The only
content left on that site is a "We have moved" page, .htaccess file,
and a robots.txt file...
...Google picked up the 301 redirects and the Open Directory update,
and quickly transferred all listings and PR over to the new site -
apparently intact. Some here on WebmasterWorld have said Google had
problems doing this, but I didn't experience any at all. But I waited
to put the 301 redirect on the old site until after I got my Open
Directory and other directory listings updated, and that may be very
important for Google."
Advice on this matter from a Google engineer
Some info on HTTP 301:
"new site" "old site" google
I trust this answers your question. If any portion of my answer is
unclear, please ask for clarification.