Tail and Ligaments
An early way to detect an impending kidding is to check the tail and ligaments. If you place your hand on the goat's spine and slide down toward the tail you should feel two pencil sized ligaments running out from the spine to the pin bone, the protruding bone on the rump. As labor nears, the ligaments will soften and eventually disappear. The area between the tail and the spine may appear sunken and the head of the tail may rise. This may occur a few hours, a few days or even a week before the actual labor, or it may not happen at all depending on the doe.
Udder
When a goat is preparing to kid her udder will start to become heavy and full, causing the bag to droop and the skin to be stretched tight. The tightness of the skin will give the bag a shiny or glossy appearance. This is a good indication of a doe about to kid, though on some goats it may not happen until a few minutes before birth. Some does may not even start producing milk until after the birth so the lack of a full udder shouldn't be used to discount the possibility of a coming labor.
Plug
Some time before giving the birth the doe will start to produce a small amount of white discharge from the vulva called the plug. It can begin up to a month before the actual kidding. When the fluid turns amber and beings to increase in flow the kidding should happen within a few hours. This is one of the surest signs of imminent labor.
Behavior
Watching for changes in the doe's behavior will give a quick clue that labor is about to, or already has, begun. A doe that begins constantly pawing at the ground may be clearing a place for a coming kid. The doe may show signs of altered behavior: a formerly social goat may become withdrawn and flighty for instance, or attempt to distance herself from the rest of the herd. A doe entering labor may appear agitated and repeatedly switch between lying down and standing up. The doe also may become noisier, making little sounds as if communicating with the coming child.