Here is what I have done.
1. Made a new folder called "child" - or whatever you want it to be
2. Made a new .css file in the "child" folder and placed this inside"
Theme Name: childtheme
Theme URI: http://www.childthemel.com.au/
Author URI: http://www.childtheme.com.au/
Tags: galleries,dual skin,three columns,shortcodes,buddypress,
REMEMBER: to change the theme details as necessary! The most important though is:
- Template: coherence - It tells the child theme what the parent theme is called.
- @import url("../coherence/style.css"); - imports the parent them style.css etc
4. When you add .css rules to the child theme style.css file, sometimes you may need to place an !important after the rule, to force it to override the parent style, but generally it will oreide the parent style.css
5. If you need to customise any of the other theme files, i.e header.php, simply copy the file to the child theme (and the file structure where needed), and edit it in the child theme folder.
Hope this helps. I know the Devs/Mods arent very helpful on this forum.