Mac OS X v10.4 and later: How to prevent .DS_Store file creation over network connections

To configure a Mac OS X user account so that .DS_Store files are not created when interacting with a remote file server using the Finder, follow the steps below:

Note: This will affect the user’s interactions with SMB/CIFS, AFP, NFS, and WebDAV servers.

  1. Open Terminal.
  2. Execute this command:
    defaults write com.apple.desktopservices DSDontWriteNetworkStores true
  3. Either restart the computer or log out and back in to the user account.

If you want to prevent .DS_Store file creation for other users on the same computer, log in to each user account and perform the steps above—or distribute a copy of the newly modified com.apple.desktopservices.plist file to the ~/Library/Preferences folder of other user accounts.

http://support.apple.com/kb/HT1629