As of 3.2 standalone isn't supported anymore

[xavier]

As per kurund suggestion, the easiest is to install a minimal drupal, then:

1. Backup your current standalone CiviCRM db.
2. If you are on 3.1.x, first install Drupal and do fresh install of CiviCRM ( same as your current version). Make sure CiviCRM works and logout from drupal.
3. Empty civicrm_uf_match, civicrm_cache, civicrm_menu table of your standalone CiviCRM db.
4. Update civicrm_domain.config_backend to null
5. In your drupal - civicrm: change civicrm dns settings in civicrm.settings.php to point civicrm standalone db.
6. Now login to drupal and go to http://example.org/civicrm/menu/rebuild?reset=1

It would be very appreciated if you detail the steps you've taken and publish that in the wiki to help others.