How to synchronize the drupal registration with CiviCRM?

Docs are the best place to go for explicit details:
http://www.openngo.org/ click on documentation.
Specific references:
http://objectledge.org/confluence/display/CRM/Synchronize+Users+to+Contacts
http://objectledge.org/confluence/display/CRM/CMS+Users+and+CiviCRM+Profile
http://objectledge.org/confluence/display/CRM/User+system+integration

(1) On a new installation:
You don't need to do anything.
Whenever a new user registers, CiviCRM checks for an existing contact with the same email address.
* If a match is found, the new user is linked to the existing CiviCRM contact.
* If no match is found, a new CiviCRM contact is created with the new user's primary email address.
Whenever an existing user logs in, CiviCRM checks for a linked contact record. If none exists, the same logic applies - either link the user to an existing contact or create a new contact. This case applies when CiviCRM is installed or enabled for an existing Drupal or Joomla site. However, we recommend that you run the batch synchronization utility (next section) in this situation.

(2) With an existing drupal user base,
If you are installing or enabling CiviCRM within an existing site that already has registered user accounts, you should run the batch synchronization utility. This utility will review each of your existing user accounts and either create or link a CiviCRM contact to each user account (that isn't already linked).

All links are off the email address.

Spam posting now.