Learning Child Theming with Twenty Twelve

Just as always, the first thing you need to do when making a child theme is to create a folder and set up a new styles.css. I created a folder called deux-milles-douze and then a blank styles.css in which I added the following:

/*
Theme Name: Deux Milles Douze
Theme URI: http://www.bluelimemedia.com/wordpress-themes/deux-milles-douze/
Description: Child-Theme of Twenty Twelve - The 2012 theme for WordPress is a fully responsive theme that looks great on any device. Features include a front page template with a its own widgets, an optional display font, styling for post formats on both index and single views, and an optional no-sidebar page template. Make it yours with a custom menu, header image (which unlike its parent will display above the navigation area), and background. 
Version: 1.2
Template: twentytwelve
Template Version: 1.0
Author: Chrstine Rondeau
Author URI: http://bluelimemedia.com

License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Tags: light, gray, white, one-column, two-columns, right-sidebar, flexible-width, custom-background, custom-header, custom-menu, editor-style, featured-images, full-width-template, microformats, post-formats, rtl-language-support, sticky-post, theme-options, translation-ready
Text Domain: twentytwelve
*/

@import url("../twentytwelve/style.css");

You’ll see that most of the information here is similar to the parent theme, but the child theme needs the last line in the comments “Text Domain: twentytwelve” and the @import call. Without these, your child theme simply won’t work.