The key to improving the soil is lots of wonderful compost.
There are several locations around the yard with compost ready to dig from years of not being cultivated. In addition, as I work in the gardens, I have compost piles near by each bed which I add to as I weed, deadhead, harvest and prune. The largest pile is covered with landscape cloth to allow the rain to be added while the moisture is retained. It is amazing how soon the piles become useful compost!
The following technique I learned from my aunt who gardened in a skirt and high heels!
There is always a small container in my sink for any green garbage that came from the earth: vegetable peels, bits of fruit and flowers past their moment. Everyday I take the waste into the greenhouse, dig a hole, put the material in and chop it up a bit. Sometimes I add water. In no time the green waste has become a wonderful part of the soil. Even I do that dressed up on my way out!
My methods may seem a bit random but it works for me. When I need compost in the yard a pile is near by. No long haul from one end of the yard to the other.
For a more traditional approach:
Composting the Easy Way by Michael J. McGroarty from his Gardening articles
Having an ample supply of good rich compost is the gardeners' dream. It has many uses, and all of those uses will result in nicer plants. However, composting can be time consuming and hard work. I place a reasonable value on my time, so spending hours and hours turning compost piles doesn’t qualify as a worthwhile exercise, at least in my book. Nonetheless, I do compost, but I do so on my terms.
I built two composting bins. Each bin is five feet wide, five feet deep, and four feet high. I built the bins by sinking 4” by 4” posts in the ground for the corners, and then nailed 2 by 4’s and 1 by 4’s, alternating on the sides. I left 2” gaps between the boards for air circulation. The 2 by 4’s are rigid enough to keep the sides from bowing out, and in between each 2 by 4 I used 1 by 4’s to save a little money. The bins are only 3 sided, I left the front of the bins open so they can be filled and emptied easily.