If you're already familiar with NetBSD, this information may not be particulary new or useful to you.  It's not particularly Atari-specific.  I do however use this for my own reference when I install NetBSD/atari.

While the current Samba 3.0 and 3.3 packages in pkgsrc currently work great on NetBSD/atari, Samba 3.5 does not. This has been noted in a Samba bug.

1. Make sure to run through the pkgsrc configuration described in the packages section.
2. cd /usr/pkgsrc/net/samba33
3. sudo make install
4. su to root when install is finished.
5. cd /etc/rc.d
6. cp /usr/pkg/share/examples/rc.d/winbindd .
7. cp /usr/pkg/share/examples/rc.d/smbd .
8. cp /usr/pkg/share/examples/rc.d/samba .
9. cp /usr/pkg/share/examples/rc.d/nmbd .
10. Test the configuration, pressing enter when prompted: /usr/pkg/bin/testparm /usr/pkg/etc/samba/smb.conf
11. To allow a particular user to log in, set their smb password: smbpasswd -a [username]
12. vi /etc/rc.conf
13. Add:
    • samba=YES
    • smbd=YES
    • nmbd=YES
    • winbindd=YES
14. Save and exit vi.
15. sh /etc/rc.d/samba start
16. sh /etc/rc.d/samba status
17. Should see the PIDs for nmbd, smbd, and winbindd are up and running.
18. From a Windows box try browsing to \\[atari name or ip]\[user name] and it should display an authentication dialog. 
19. Log in with [machine name]\[user name] and your password.
20. Browse to the share named after your username.
21. Observe it's possible to copy a file to the share and back.
22. sh /etc/rc.d/samba stop
23. To reboot and have Samba run automatically: shutdown -r now