I have a cutom module which creates a page with a custom form.
the problem is that i don't print whole form at once like :

    $form = drupal_get_form('custom_example_form', $adverts);
    print render($form);

Rather my code is like:

    $form = drupal_get_form('custom_example_form', $adverts);
    print render($form['name']);
    print render($form['descriere']);
    print render($form['submit']);
    print render($form['form_id']);
    print render($form['form_build_id']);

The problem us that is second example drupal is not generating 

    <form id="" accept-charset="" method="" action="">

How do i generate <form> in second situation?