Kinda depends on what you want to spend and how preventative you want to be.
You could go all out and get one of these -
http://www.autosportcatalog.com/index.cfm?fa=p&pid=3962&sc=58446&adpos=1t1&creative=11114173878&pc=TERKHFHY&gclid=COK_nOHfmK8CFeYRNAodOlZ2wwThat'll prevent pretty much any rusting from moisture/condensation, and should also keep out rodents/bugs/pests...
At the least though you should probably remove the wheels so that the tires don't flat-spot - granted if the car is going to be sitting for a while, it'll probably need new tires before you get her out again anyways. Put jack stands or blocks beneath each lower control arm - I seem to recall that you DON'T want to leave a car's suspension unloaded for extended periods of time. I'd also remove the battery as A) you don't need it there and B) they can leak corrosive acid in rare-but-plausible scenarios. Lastly I'd at least attempt to blow out all the coolant from the heater core, as it can deteriorate into sortuva sludge which could plug up and essentially ruin the core.
And of course you can cover it, but be careful what you cover it with, as covers can trap moisture, dirt, and other unwanted materials against the paint. It can also cause scratching as it gets bumped/nudged/blown over the years, depending on what the cover is made of. I typically
don't cover my car during winter storage because it's no-big-deal to hose it off in the spring and she's good-as-new.
That's my
...
