What is the best practice for managing disabled users? Should these be imported in SharePoint? And if not, how to filter these records?
SharePoint 2013, Synchronization option in User Profile Service
If the users have already disabled from Active directory and you need to exclude them in SharePoint , you should do the following
Centeral Administration > Application Management > Mange Service Application > Manage User Profile Service .
Below Suncronization > Configure Syncronization Connection.
UserAccountControl Bit on Equals 2
you can filter the Disbaled user from User Profile Sync using the Connection filter as M.Qassas Mentioned in his post.
The User Profile Synchronization timer job marks for deletion users who have been deleted from the directory source. When the My Site cleanup job runs, it looks for all users marked for deletion and deletes their profiles. Respective My Sites are then assigned to the manager for the deleted user and an e-mail message notifies the manager of this deletion. All this is handled when you have MySite Cleanup timer Job enabled.
In Most cases companies loses the mysite of disabled user due to this. In that case(if you have mysites in your company), Disabled MySite Cleanup timer Job and manually delete the User from the Profile Store, along with set the connection filter.