Opinions will vary on these topics. Here are mine:
If parked for extended periods, run the generator under load, AC in summer/heat pump in winter (or electric heat as appropriate for your rig) for at least 1 hour per month. Start the generator and let it warm/cool the rig while you check the engine oil, kick the tires, dust the cobwebs or whatever. Take the MH for a drive once a month for a 30 minute drive. This will fully warm up the engine, transmission, roll the tires, wheel bearings, and shake up the mice. IF, for some reason driving for 30 minutes is impossible due to weather etc. I would NOT start the MH engine. I'd simply let it sleep. If it can't be fully warmed by driving, don't start it at all.
If you're parked on grass put something under the tires. Pieces of plywood are great. Something to stop the inevitable sinking and the dirt contact. If you can find them on a great sale, plastic cutting boards are good too. Depending on your circumstances, they may even be cheaper than buying a sheet of plywood, saw horses and a skillsaw to make plywood pads. ;D
Now the best part, here the opinions will vary widely and gain religious fervor. Whether you need to cover your tires or not all depends. If I was in the south where the sun was shining everyday and was parked for months without moving, I'd probably cover them. But, if I was parked in WA state where it rains steadily for months on end, and is cloudy and overcast when it's not raining, (yes I lived there full time for 53 years) then I wouldn't bother. I'd spray liberally with 303 and just recoat as needed. I'd be careful to spray everywhere I could, between tires, backsides etc.
The other item that I'd mention is to use everything as often as possible. Even if you can't go somewhere, turn on the heater, water heater, lights, tv antenna, water pump, close out cover etc. Things that don't get used tend to stop working more than things that get regular use. Even if it's only once a month, try to exercise everything. Also, if you find something that doesn't work when you're just there checking, it gives you time to get it fixed before you need it.
Ken