Improving your soil is pretty easy. In the fall, after I harvest, I spread out a layer of mulch (we'll get to that next time), and then cover with newspapers, and then another layer of mulch or straw to help keep the paper in place. It not only keeps the weeds out, but over the fall and winter months, the mulch and paper will break down, and can be tilled under in the spring. You can add some manure and a little peat moss to make a rich garden soil. If your soil is pretty thick and wet and impossible, like mine, then you may consider raised beds (we'll get to those in a couple of days). You can control the soil and the weeds easily and the vegetables I grow in the raised areas are always very healthy and productive.
Another thing I do in order to prepare my ground and soil for the next planting is season is to lay out a tarp across the area I will want to use for planting. I cover the entire area and then lay bricks or some other heavy objects on the outer edges of the tarp to keep it down. A black tarp is best, but not necessary. You can also lay a thick layer of hay or straw on top and then use that to work into your compost or garden later. The tarp helps keep the ground warm, and kills off all of the weeds. Then, when you're ready to plant, you just peel the tarp back, layer the soil with any compost, manure, or peat moss, and till it under.
By the way, the West Ladies have a garden soil segment on their DVD The Art of Gardening, that is very helpful!