WEB silly questions - 404 page help

What do I need to have in the header of my custom 404 page? I'm trying to make absolute certain the search engines know this shit is a 404 and will stop indexing.

I've added

Code:

ErrorDocument 404 /404.php

to my .htaccess and

Code:

<meta name="robots" content="noindex, nofollow">

to the header. Anything else I need to do?

Thanky