I currently use a Nikon D300 and have used this camera for just over a year, before this I had been using a Nikon D90. For my previous course with the Photography Institute (PI) I learnt a great deal about the operation of the camera. Prior to the PI course I had never even used the camera on manual. Shutter and aperture priority modes were the order of the day. The PI course gave me the confidence to take full control of the camera.
As recommended in the course notes I dug out the instruction manual and read through it again to brush up on my knowledge of the operation of the D300. It was surprising what I learnt from doing so, the extra knowledge I had gained from the PI course, made some of the parts of the instruction manual make sense, I obviously glossed over these bits when I read it the first time!!.
My most commonly used setting for the D300 is aperture priority (A) as most of my photography to date has been either portrait or landscape where I like to be in control of the depth of field. Having said that in landscape photography I do like to use a manual setting (M) as well, instead of using the exposure compensation in A mode if i want to over/under exposed the photograph.
I have done a small amount of the motor sports photography and for this I have used shutter speed priority (S).