You'll make lots less work for yourself next spring if you begin your new garden beds in October. If the area is in lawn, cut the grass low, then cover the ground with several layers of dampened newspaper topped with several inches of mulch, compost or manure. By spring the sod will have decomposed and you can dig in the organic matter, add any needed amendments, and plant.
As you empty annual beds this fall, there are two main ways to enrich the soil for next year: spreading compost or planting cover crops. Before you spread compost, dig or lightly till in any plants that aren't diseased to return nutrients to the soil. Spread compost, even if it's not well decomposed yet. It will protect the soil over the winter and break down by spring planting time. Or you can plant cover crops, such as buckwheat or annual rye that will grow this fall and early spring until you till it under several weeks before planting.
Ok, ok, so maybe the weeds have already taken over. Don't give up. Get them out of your garden or else they will make it doubly hard for you next spring. Since bare soil invites weeds, cover bare soil with mulch, such as layers of wet newspaper covered with straw, compost, or manure. This will control late fall and early spring weed growth and provide organic matter.
Plant garlic now for harvesting next summer. Purchase garlic sold specifically for planting, or buy organic garlic. Commercial, non-organic, supermarket garlic may have been treated to inhibit sprouting. Break the garlic head into individual cloves, keeping the largest ones for planting. (Use the small cloves for cooking.) Plant cloves about three inches apart with the pointy side up. Try some different varieties to see which you prefer. Mulch the bed well with straw.