I have tried to create a child theme for twentytwelve exactly as prescribed:
1. created new subdirectory /wp-content/themes/twentytwelvechild
2. Created 'minimal' style.css file:
Theme Name: Twentytwelve Child
3. FTP'd this file into the above subdirectory
But when I look in 'manage styles' the child theme is not there. What am I doing wrong?