Use SendSong, iToner etc to install your custom Ringtones first.

You will need Mobile Finder or any terminal. Finder is very easy to use. Install it through Installer.app.

After the ringtones are set, open Finder and navigate to ~/Media/iTunes_Control/iTunes/. Click on iTunesRingtones and click Modify (if you don't see it, skip this step). Remove all Write permissions. Go back to the list and do the same thing to Ringtones.plist.

Wala~ Sync the phone with iTunes and the Ringtones will remain!

Remember to enable Write permissions for both files before you use SendSong or iToner to add Ringtones.

I followed the address but inside ~/Media/iTunes_Control/iTunes/. I don't see iTunesRingtones to click. I see Ringtones.plist but there is no iTunesRingtones. Why it is not there and what should I do tohave it there?

You have to add custom ringtones first. If you still don't see, skip this step.

cant get this to work on my 1.1.1 Its as if the settings I choose in the mobile finder doesnt work.They arent saved