First try a good squeeze type blower, the Giottos "Rocket" type have a filter for the air intake. I've used a standard type bulb blower, no brush. Open the shutter in "Sensor Clean Mode" and see if it will just bow off. If that does not work, I use the Eclipse wet-cleaner and wipes.
If you use older lenses, change lenses often- make sure the mount of the lens is clean. I cut way down on debris getting into the camera by making sure the threads of my older Thread Mount lenses are clean, and mount them on the M adapter before putting onto the camera.