In my experience, studded tyres do make all the difference on ice and hard packed snow, as stated already. I have Nokian W106s myself and they seem to do the job for me.

Winter cycling is different in many aspects and will probably require adjustments in your riding anyway. For me, spinning seems even more important than in summer conditions. If you have found the joys of layered clothing, you are all set in that department. Personally, I don't like clipless pedals in winter, I prefer proper winter boots and platform pedals. But that depends on your riding temps and is also a matter of taste. Keep lower pressure in your studded tyres than you would otherwise. It will add to rolling resistance, but it'll help with grip and dealing with icy ruts.

Depending on your route and climate, have a plan B ready for your transportation. Even the simplest mechanical problems (replacing a flat tube for example, ask me how I know) can be really difficult to fix if it's cold, dark and snowing. At the very least carry extra clothes so you can walk a bit if needed. That's another reason why I prefer shoes without cleats in winter.

You need good lights in the dark. Modern LEDs are very good, but batteries are nuisance in cold temps. Again, personal preference, but I "upgraded" to a dynohub based front LED a couple of winters ago, and haven't really looked back.

But these are really MY solutions. You cannot know what suits YOU before you try out yourself. Happy winter riding!

--J