Creating Permanent Custom Fields

Hey,

I am designing a blog for my sister and I’m just wondering how to implement permanent custom fields, that always show up (i.e., when you make a new post, they are there) without having to go through the custom fields menu. Is there a backend trick to this? I know sites that do it, see caughtya.org — the site is WP-powered and utilises custom fields that always show up. I am pretty adept with PHP (clueless about MySQL).