theming a CCK input form
Your steps are right. I tested it on my local environment, and it works.

For example, for the content type "companynews", add the function to the template.php:

function garland_theme($existing, $type, $theme, $path) {
  return array(
    'companynews_node_form' =&gt; array(
      'arguments' =&gt; array('form' =&gt; NULL),
      'template' =&gt; 'node-companynews-edit'
    )
  );
}


Create the node-companynews-edit.tpl.php file and put the test code.

&lt;?php
  echo 'it works!";
?&gt;


Clear the cache, and access http://example.com/node/add/companynews: it shows "it works."

PS: You can also use hook_form_alter() to alter the form, and then use CSS to style it.