The Nikon SB-600 Speedlight is designed to be a stand-alone i-TTL flash, or a Remote wireless slave flash for the CLS system. It does not have a Master mode like the SB-800 does.
It is a simple but powerful Speedlight flash, and does a great job as a slave for your D300 and a commander device to control. Let's look at the configuration method for the SB-600. It is quite different from the SB-800.
Setting Remote Mode on the SB-600 Overview of Settings:
Turn the SB-600 on with the ON/OFF button on back.
Hold down the ZOOM and Down-buttons for about two seconds.
Use the MODE button to turn Remote mode on.
Hold down the ZOOM and Down – buttons for about two seconds again, and the flash will switch to ...