This is question which people are asking quite often. The attribute which is controlling behaviour is userAccountControl attribute. You can list disabled users from AD by following methods (my favourites):

ADUC:
ADUC saved query can return results using the following query;
(&(objectCategory=person)(objectClass=user)(userAccountControl:1.2.840.113556.1.4.803:=2))

Dsquery
dsquery user -disabled (dsquery has some limitations, example by default it shows only 100 first users)

PowerShell
Search-ADAccount -AccountDisabled -UsersOnly | FT Name,ObjectClass -A