[Samba] some permissions issues

[CPDead]

I´m facing some troubles with file / directory permissions...

I log on the domain as admin user(root), and theres a pub share, on witch 
everyone needs to have permission to create / modify files, but when I 
change or create a file, only root can change the file, no one else. And 
then i need to go to server to chgrp users * -R and chown nobody * -R to 
allow others users to change the file.

can someone give-me a clue with this ?