Empty and flush out your holding tanks (if you haven't already done this upon completion of your last trip) at your nearest dump station! 

Step 2. 

Drain your fresh water tank and your water heater (leave the drain plug out of your water heater until spring). Your water heater will drain a little faster if you open a couple of hot water taps in your unit! You shouldn't open the safety valve on your water heater to help drain it because it might not seat properly again and can be an unnecessary expense when you need to replace it in the spring!!! 

Step 3. 

By-pass your water heater - you don't need to run any antifreeze into this.

Step 4. 

You are now ready to put some RV (non toxic) antifreeze through your RV plumbing system!! Some books or people will tell you to put 6 or 7 gallons of antifreeze into your fresh water tank, I strongly recommend that you do not do this as it is a complete waste of money! 7 gallons of antifreeze would cost you about $30.00 to $40.00, you should only need 2 gallons (maybe 3 for some of the larger units) and most of the time you will have approximately 1/2 of one left over! It is best to disconnect the water line from your fresh water tank at the pump side and use a separate suction line which some rv parts departments have already made up for about $4.00-$6.00, or a pump winterizing kit consisting of a brass three way valve and suction line which stays attached to your pump permanently, about $18.00-$25.00. Stick the suction hose into the jug of antifreeze making sure it goes all the way to the bottom of the jug, with all your taps turned completely off and your water heater by-passed, turn on your water pump and open a water tap (hot or cold) (the farthest one from the pump) And wait until you see the antifreeze come out at a steady flow, turn off that tap then do the next tap and so on until you have done them all, don't forget to flush your toilet until it comes out steady there as well! If your unit has an outside shower don't forget it as well! (Sometime during the process you probably had to switch jugs when the first one ran empty) next poor some antifreeze (you should have some left) down each sink drain and your tub or shower drain (about 1/2 a cup), to ensure your p-traps don't freeze up! Turn your pump switch off and clean up any antifreeze over spray left in your sinks and tub or shower, open all your taps and toilet valve by sticking something in the hole (make sure it doesn't fall into your tank) I find a toilet cleaning brush is the best thing to use! That's it you're done! That wasn't so bad was it? Now remove your batteries for winter storage!