How does Drupal know which Entity View Mode to use?
With a tiny bit of glue code you can use specific node template files for different view modes, so they can become pretty useful:

function MYMODULE_preprocess_node(&amp;$vars) {
  if($vars['view_mode'] == 'some_type') {
    $vars['theme_hook_suggestions'][] = 'node__' . $vars['node']-&gt;type . '__some_type';
  }
} 


That will allow you to use template files with names like node--article--some-type.tpl.php specifically targeted to that view mode.

Other than that MPD's answer has all of the other common cases covered.