Install the following packages :

$ apt-get install winbind samba

Join the domain :

$ net rpc join -u Administrator -S "server"

Fetch the correct (Windows) domain name :

$ wbinfo -u

If you see the list of users, it's ok. Verify if there is winbind entry in /etc/nsswitch.conf

Put it in the /etc/samba/smb.conf config file

You can use the following PAM resources files :

auth required pam_winbind.so
account required pam_winbind.so
auth required pam_securetty.so
auth required pam_nologin.so
auth sufficient pam_winbind.so