I searched for similar questions on this issue but found none related to Mac OSX.
Situation:
Trying to test android apps on a Galaxy S (D
USB driver problems happens under Windows.
For MacOS, I had nothing to do : ADB found my device.
You don't need tethering : it's for sharing an Internet connection.
USB Debugging is needed. Also make sure you authorize your Galaxy to use Unknown sources (@ Applications -> Unknown sources (it's a check box)).