Growing plants, grass, vegetables and other items is difficult enough for some individuals without compounding the situation with clay soil. This type of soil, although nutrient-rich, does not drain and can become as hard as a rock when dry. If you live in an area that requires you to work with this medium, you can change its texture and make it easier to deal with.
Till up the top 6 inches of soil, so you can mix in other materials. Do not water before doing this; in fact, wait for a dry period. Wet clay equals a muddy mess.
Spread organic materials such as mulch over the tilled area to slowly releases nutrients into the soil.
Spread a couple inches of topsoil over the tilled area to add richness to the dirt and make it more workable.
Spread 3 inches of sand over the tilled area to improve drainage of the clay and keep it from sticking together in hard clumps.
Till the soil again to mix it all together.
Unless this is for a lawn, turn the soil every year and add in new organic material, old plants and more topsoil.