[K12OSN] file permissions for different groups?

[Krsnendu Dasa]

I have a directory with files inside.
I want staff to be able to view it but not write.
I want admin group to be able to read or write.
Noone else should be able to access it.

How do I do that?

Also I have a WinXP user who copies files to our samba server. Every 
time he copies something it is rw only for owner not group. How do I set 
it up so that when he copies files it is always rw for admin group?

Thanks.

Krsnendu dasa