help creating and configuring custom post template

I'm having trouble making an additional post template to format some posts differently than the default posts.php. My research has involved the WP codex, WP Tuts.com, and even attempting to make my own plugin - all to no avail. Can anyone help me out? I'm working on a site using a child theme of the Hatch theme. Thanks in advance for your time and consideration advice.

-William