There are several different solutions. The best one, both from SEO and User perspective, is the one-to-one 301 redirect. It preserves your link juice and at the same time redirects the client to the exact location on the new website.
If you have mod_alias enabled, I would suggest a simple
RedirectMatch 301 ^(.*)$ / http://new.domain.com/$1
The result instruction can be accomplished with
RewriteEngine On
RewriteRule (.*) http://new.domain.com/$1 [R=301,L]
The second one is the best choice if you need to chain multiple conditions and filters. For example, if you need to redirect only certain hosts or clients depending on User Agent header.
Remember: mod_redirect takes precedence over mod_alias.
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