Here is a quick and dirty for Winterizing your RV.
1. If you have an Ice maker you need to disconnect the control valve inlet and outlet lines.
2. Remove the ice maker filter and drain it.
3. Washer/dryer; pull hoses from washer and drain it, Actually run washer thru cycle to cause it to open it's valves - See MFG winterizing instructions
4. Pull drain plug from water heater and then open blow off valve to drain
5. Open the drain valve for the Potable water tank.
Now the fun part:
Get your self an air compressor and set it to 25psi, get the correct fittings to connect it to the City Water hose connection.
6. Open the kitchen faucet on the hot side and then the cold side until air come out and then shut them.
7. Now repeat this for every faucet and toilet working your way to the back of the coach, don't forget the shower and the Outside Shower.
8. Once this is done leave all the faucets open, this allows for expansion if it freezes.
9. Now you can disconnect the air compressor.
10. Now you can take your MH to dump the Sanitary tanks.
11. Now get yourself a gallon of the RV anti-freeze and pour some down each sink, just enough to fill the drain traps, also down the shower and pour the rest of it down the toilets.
This is all it takes for the average MH to be Winterized.
Hopefully this helps.