Moving a Domain, how to insure SEO - see Bruce Clay's SEO Web Ranking page

Your main concerns are that you'll likely lose your page rank in Google and other search engines for a bit until they find the new site, and that you
need to get all those bookmarked or links to your site to the right place on
the new site. It's easiest not to change your URL, but if you have to, here
are a few things you can do:

Create 301 redirects in your htaccess file to direct any of the incoming
traffic on the old URL to the new URL.

And find out who is linking to you, for the biggest traffic, and let them
know to change the URL.

Advertise the change to the URL via blogs etc to your target audiences to
let them know to.

Don't panic when you see that drop in rank for a while.

Finally, Bruce Clay is one of the big names in search engine optimization
and he offers some nice tools on this site, including a tool to track who is
linking to you.

http://www.bruceclay.com/web_rank.htm
Good luck.

Susan Fariss
SRA Touchstone