Documentation

/**
 * Returns the exposed filter widgets for a view.
 *
 * @param mixed $view
 *  Either a string with the name of the view or an object of the view
 * @param string $display_id
 *  An optional string with the name of the display for the view.
 *
 * @return string
 *  The themed exposed filter form.
 */
function embed_views_exposed_form($view, $display_id = '') {
To figure out the id of a display, look under Other, in the view edit page for the particular view that will be embedded, for Machine Name what ever this name is is what should be used for the $display_id variable.

Usage

Simple version of code to embed an exposed filter.
  print embed_views_exposed_form('test', 'embed_1');
Embedding a view's exposed form for an alrady created view using the embed_views_exposed_form() helper function.
  $view = views_get_view('test');
  $view->set_display('embed_1');
  print embed_views_exposed_form($view);

  ... some other code ...

  $view->destroy();
Embedding a view's exposed form for an already created view using the display's embed_views_exposed_form() helper method.
  $view = views_get_view('test');
  $view->set_display('embed_1');
  print $view->display_handler->embed_views_exposed_form();

  ... some other code ...

  $view->destroy();