A lot of what you do depends on your planned use of the tractor in the winter: storage or limited use.
It would be best to run it to operating temp once a month. That removes moisture from the engine & fully charges the battery. But, if that won't work, remove the battery & keep it indoors w/ a float charger on it every 2 or 3 weeks. Do not let the battery sit uncharged for more than 30 days. Fill up the gas tank w/ fresh gas & Sta-Bil. If you are not going to use it at all, drain the tank & leave the cap loose; the ethanol in the gas will not store very well! Remove the plugs, put a tablespoon of oil in the cylinders & turn the engine over a few times to lubricate the cylinder walls. Block the clutch. Check tire pressure & add air if needed. Put it on blocks or jack stands to keep the tires off of the ground. Plug the exhaust pipe to keep the mice out. If mice are a major problem, soak some cotton balls in peppermint oil & put them under the hood & around the radiator. Some folks say mothballs work just as well. Change the oil & lube it. Make sure the hydraulic fluid doesn't have water in it. Check the anti-freeze; use 50/50 anti-freeze & distilled water & run the engine to make sure it is well mixed. Donít drain the block & radiator; all that gets you is corrosion & rust build-up in the water jacket. If the tractor is not kept in a shed or garage, I don't think putting a tarp over it gets you much. A car cover, which supposedly does not retain moisture, would be a better idea.
Most all of this is covered in the owners manual, chapter III, storage.