If your rig has a refrigerator with an ice maker, the solenoid valve that allows the water to flow into the ice maker must be emptied. Determine the voltage required to activate the solenoid...mine is 110 VAC...disconnect the outlet side of the valve and apply voltage.
Also the filter of your water pump must be emptied, because the filter is plastic. In fact, RV antifreeze (NEVER radiator antifreeze) should be pumped through the pump.
One of the most vulnerable parts to freeze breakage is the valve of the toilet, which is also plastic. Make sure it gets emptied as well as the spray hose of your toilet is so equipped. Also empty the shower hose, if it's a telephone shower.
If you are concerned about odor in the holding tanks, run some bleach in them, fill the tank then dump prior to winterizing. Add a small amount of antifreeze into the holding tanks to cover the dump valves to keep them from drying out.