Battery maintainer is the most important piece of advice.

I do start the car once per month - keeps seals and other parts lubricated which prevents their corrosion over long winter months. Since I bother to start it, I also vary the throttle and let it get to operating temp, though this is not needed for lubrication. This is a little controversial, but my head Porsche mechanic recommends it.

If you garage the car, there's no need for a cover.

I would NOT apply the handbrake over the winter - park it level and leave it in gear or use stops on the wheels.

I also roll the car once every 4-6 weeks to prevent flat spots on the tires.