I maybe a bit kiasee, but I switch off camera, switch camera to mf, then switch ring on lens to mf, and then turn on camera. I dunno if the lens is un-coupled from the AF drive of the camera if only the ring is switched to M, so i don't want to risk spoiling the AF motor and so switch both to MF.
Techncially, it is not necessary to deactivate the AF control on the body when using the AF 105mm f/2.8 Micro-Nikkor. The AF to M switch on the lens engages focusing control on the lens itself in the 'M' mode and this does not affect the screw-drive on the lens mount. In the 'AF' mode, all focusing control is transferred to this little AF coupling slot and is driven by the camera's AF motor. If you look at the lens mount itself, you will notice the drive coupling slot (at a 4 o'clock position if you look at the lens rear mount with the white mount alignment indicator at the 12 o'clock position) does not rotate when you focus the lens manually. This is because the focusing screw is decoupled within the lens in the 'M' mode and will not transfer any focusing ring rotation through to the camera.
However, with either the 'S' or 'C' mode activated on the body, the moment you depress the shutter release lightly, you will still activate the AF motor. The motor will run in a no-load condition and although it does not disrupt the lens manual focusing ability, it does consume battery power. So it would be advisable to switch it to the 'M' mode to conserve batteries.