If you want to move your website to new domain without hurting its SEO then use 301 redirect. Most simple way to do this is using htaccess mod_rewrite.
A wrong way
Most webmaster uses following htaccess rule to move their website but this is a wrong way. This rule redirects each page on old domain to root of new domain (eg: http://olddomain.com/page.html to http://newdomain.com/) that affects indexed pages in search engine. This is not a SEO friendly way so I will not recommend it.
SEO friendly way
This is the best way also recommended by Google