To hide individual menu items in the admin panel you can use a number of plugins or just use the function unset() to remove elements of the global array $submenu.

I think an example should make it clearer.. On my test site in the theme folder in the file functions.php paste the code:

function remove_submenus() {
  global $submenu;
  //Dashboard menu
  unset($submenu['index.php'][10]); // Removes Updates
  //Posts menu
  unset($submenu['edit.php'][5]); // Leads to listing of available posts to edit
  unset($submenu['edit.php'][10]); // Add new post
  unset($submenu['edit.php'][15]); // Remove categories
  unset($submenu['edit.php'][16]); // Removes Post Tags
  //Media Menu
  unset($submenu['upload.php'][5]); // View the Media library
  unset($submenu['upload.php'][10]); // Add to Media library
  //Links Menu
  unset($submenu['link-manager.php'][5]); // Link manager
  unset($submenu['link-manager.php'][10]); // Add new link
  unset($submenu['link-manager.php'][15]); // Link Categories
  //Pages Menu
  unset($submenu['edit.php?post_type=page'][5]); // The Pages listing
  unset($submenu['edit.php?post_type=page'][10]); // Add New page
  //Appearance Menu
  unset($submenu['themes.php'][5]); // Removes 'Themes'
  unset($submenu['themes.php'][7]); // Widgets
  unset($submenu['themes.php'][15]); // Removes Theme Installer tab
  //Plugins Menu
  unset($submenu['plugins.php'][5]); // Plugin Manager
  unset($submenu['plugins.php'][10]); // Add New Plugins
  unset($submenu['plugins.php'][15]); // Plugin Editor
  //Users Menu
  unset($submenu['users.php'][5]); // Users list
  unset($submenu['users.php'][10]); // Add new user
  unset($submenu['users.php'][15]); // Edit your profile
  //Tools Menu
  unset($submenu['tools.php'][5]); // Tools area
  unset($submenu['tools.php'][10]); // Import
  unset($submenu['tools.php'][15]); // Export
  unset($submenu['tools.php'][20]); // Upgrade plugins and core files
  //Settings Menu
  unset($submenu['options-general.php'][10]); // General Options
  unset($submenu['options-general.php'][15]); // Writing
  unset($submenu['options-general.php'][20]); // Reading
  unset($submenu['options-general.php'][25]); // Discussion
  unset($submenu['options-general.php'][30]); // Media
  unset($submenu['options-general.php'][35]); // Privacy
  unset($submenu['options-general.php'][40]); // Permalinks
  unset($submenu['options-general.php'][45]); // Misc
}
add_action('admin_menu', 'remove_submenus');

The code is workable, a hitch may be if you have already installed third party plugins and they added an item to the admin menu. In such cases, you can use the array output function var_dump() and see which items need to be removed.

An example of viewing the menu list in the admin panel:

function remove_submenus() {
  global $submenu;
  echo '<pre>';
  var_dump($submenu);
  echo '</pre>';
}
add_action('admin_menu', 'remove_submenus');