How are crop circles formed?

They are normally made by using planks of wood and rope as a giant compass. One person stands in the middle of the to-be formation and acts as the pivot by holding one end of the rope as the other(s) stamp down the pliant wheat with the planks at the other end of the rope. Crop circles appear most often at night after rainfall as the wheat is easy to bend without breaking when it is moist. More modern and elaborate ones seem to have been made with the help of GPS units. It should be noted that vandalizing some poor farmer's crops is highly illegal... and farmers often have shotguns and low tolerance for such vandalism. Farmers have it rough enough. I hope you weren't asking for instructions on how to break the law!