Collapse the menu fieldset by default

Within your template.php file enter the following:

function yourthemename_node_form($form) {
 // Collapse fieldsets
 $form_elements = element_children($form);
 foreach ($form_elements as $element) {
 if ($form[$element]['#type'] == 'fieldset') { //Identify fieldsets and collapse them
 $form[$element]['#collapsible'] = TRUE;
 $form[$element]['#collapsed'] = TRUE;
 }
 }
 return drupal_render($form);
 }