I tend not to use all of my raised garden beds during the winter. The garden is much smaller and compact, needing only two or three beds at most. For the garden areas not being used, I put them "to bed" for the winter and they are the first ones I use come spring.
I start by turning over the soil and adding a layer of compost.
I also add a layer of wood ash (from our fire pit) or some Azomite for an additional boost of nutrients.
Once all of this is worked into the soil, I'll cover it with 2-3 layers of cardboard. This will break down over the winter and the earthworms LOVE IT!
Last I'll add 4-6 inches of wood chips. If you see any tree trimmers in your area, they'll dump a load of chips in your yard for free!
Come spring you'll have a beautiful, nutrient rich bed
to plant your seedlings in. And no weeds since the cardboard and thick layer of wood chips will snuff them out in the spring!