First off, how much land? If its acres then its out of my area of knowledge. I just dig up the grass with a good shovel and take off the first several inches of clay. Then i add things like composted cow manure, peat and maybe some sand if its not sandy already. Here in Indiana we have plenty of clay. We must be one of the worlds top clay pot suppliers. Lol.
Anyhow then i till it in again and again. If i am not satisfied by the color i add some more good stuff and till again and again. Make sure you have no low lying areas. Last year i did not build up high enough and lost a few starts to heaving and rot.
But if you have a lot of land, rent a tractor or backhoe. Good luck.
