Regularly use a rocket blower on the mirror and camera chamber. For dust to get to the sensor, it must first pass the mirror and camera chamber (even if it is coming from within the camera). Any dust particles that you remove from the camera chamber means less potential dust sources for the sensor.
I will be uploading a post soon compiling all the information that I have learned from a myriad of other Nikonians's posts over the months. This post will include techniques to see the dust, preventative measures, both dry and wet sensor cleaning methods, along with a list of sensor cleaning tools and products.
This post will also put the dust issue into its proper perspective, so that others do not experience needlessly the anxiety I did about the D600. While I was waiting for the D600 to arrive, I read a post about a new D600 with a finger print on the mirror, plus dust and oil on the sensor. I was a bit upset to say the least. I thought if my D600 was like this when it arrived, I would return it to B&H and continue to use my D300.
Happily mine was in good shape. Out of the thousands of the D600 sold, we only hear about the relatively few problem cameras. Concentrating on the few bad ones makes the problem sounds worse than it really is.