assuming the D300 has some common ground with D80, if you use it manual centre exposure, by waving it around a frame, you get an idea of correct exposure for the important bits. Having then taken one, look at the replay and rotate the knob until you get to a mode that shows 'highlights'; if a significant area is flashing, stop down and retake. Shoot RAW and you can sort out any underexposure, globally or locally, in Capture NX (see thread in Digital Dargroom)

This is one of the key techniques to grasp on landscape photography as the problem of huge range of exposure is so common. Others might recommend HDR, but will leave that to them.