I'll post my two cents worth. I winterize it with antifreeze, then drain the antifreeze and blow it out. Anti freeze in traps. Drain and flush water heater. Leave roof vent open a little. As far as battery, I have a main battery disconnect and wired in a float battery charger with a separate connection for a lightweight cord.
That way I can run a lightweight (and much less expensive cord than my 30 amp cord) cord out in the snow all winter and not have my converter (I replaced my WFCO which never worked quite right) powered up all winter.
The antifreeze/blow out may be overkill, but doesn't take that much longer and is easier than a broken water or faucet or having a connection fail and pink stuff all over while closed for the winter.