The very nature of clay soil--sticky, heavy and compact--makes it very difficult for anything to grow. Roots can't penetrate clay soil and air can't flow through it. There are different ways of fixing clay soil in a yard and all of them require adding large amounts of organic material. Wait until the clay soil is dry before working it and use 2 to 3 cubic yards of organic material or other amendments for every 100 square feet of gardening area. Begin this process in the fall.
Till the soil to a depth of 12 inches, turning over the soil as you go and crushing any large clumps of dirt. Remove any rocks, roots or other debris.
Add a 6-inch layer of coarse builder's sand and a 2-inch layer of compost over soil. Use your garden fork to mix the materials together.
Rake the area until it is level.
Spread a 6-inch layer of wood chips or shredded pine bark over the top of the soil and water deeply.
Wait until spring and then mix the wood mulch into the soil and you are ready to plant.