I drop the tanks, will flush the black some if there's not a line waiting on me. While the gray drains I'll drop four toilet bowls of water and my drop in black tank sanitizer. That's pretty much it for the tanks.
I carry about 1/3 tank of fresh at all times for use on the road but if it's going to be stored more than a month I'll drop that out once home.
I've always left the water system full during warm months. Some folks drain their water heater and drop the low point drains but I've not done that.
I've got a battery disconnect, I'll turn it off if I know it's going to sit more than a month.
LPG off soon as I close it up too, close the blinds to keep the sun out, lube the slide seals.
That's all I do to prep it for summer storage. I'll go out every few weeks to run the slides out and check for leaks, bugs, etc. Plus I just like to visit.
Once the batteries get down to 2/3 I'll plug in to let the converter recharge them.
Cover the tires if you can, that will increase their life.
Same things in winter except I'll drain the water system, run antifreeze through everywhere including a few gallons of antifreeze into the black tank and one gallon in each gray tank to protect the pipes near the valves. If you endure serious cold take your batteries out and put them in climate controlled storage.
Check the tire pressure every so often, if you're really industrious you can jack each wheel up and spin it to a different position every 4-6 weeks. That prevents flat spots.
That's it in a long nutshell. Nothing big or complicated if you stay on top of it.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10