Mines in a shed but this is what I have done.
Place a tarp or better yet plastic drop cloth under it. This helps keep moisture from collecting under it and rotting it out. I also park it on some scrap wood. I dunno if this helps perserve the tires but it does keep the tarp from sticking to them.
I fill the tank and put stabil in it. I also change the oil so that the old stuff isn't sitting in the pan all winter. Throw a few dryer sheets in the interior. This is supposed to keep mice out but it also makes it a bit less musty come spring. Since its going to be outside I would probably keep the snow off of it and away from it. snow mounded up around it traps moist air up against it. Air circulation is good. Some people put steel wool in the exhaust. This allows the pipes to breath but still keeps critters out. I don't do this but mice aren't an issue for me.
Theres some debate on wether you should start it or not. I leave mine off untill its ready to be woken in late march. If you do decide to routinely start it you should let it get up to operational temp before you shut it down. Some argue that this can't be done with just idling so you should drive it.
My start routine is pretty simple. I reinstall my battery but disconnect the coil wire. I then crank the engine a bit to ciculate the oil. Then I reconnect the wire and fire her up, let her idle, and drive her easy until I've burnt through half a tank. Oh and I change the oil ASAP.
Hope that helps a bit.