Here are some signs to watch for:
Udder: It will become noticebly larger within 24 hours of kidding - make a habit of checking that udder each day
Tail Head (part of the spine between the top of hip bones and where the tail joins the body): It will start to hollow out on each side, and if you run your thumb and fingers on either side, from hip to tail, you will find that all the ligaments begin to disappear as labor draws near. It's good to start practicing this by comparing a non-bred doe to a pregnant one. When in labor it usually appears that the tail head is raised upward.
Back Side: As pregnancy progresses the does start "springing" - the vulva area starts to swell and jiggles as they walk. It will be puffy and wrinkley at the same time. When the does are in labor, instead of being swelled outward, it is pulled inward.
The doe will become much thinner looking and flanks will hollow out (unless she's loaded with kids)
Signs of labor: Does usually will hide out or try to get away from the herd. They will do a lot of pawing (actually plowing :lol), stretching, "talking", and as they have contractions, they might stand on tippy toes, hunch up, and will pull their tails over their body. They do a lot of squating, they might pee and they might just squat until the contraction subsides. Sometimes the first sign of not feeling well is that they don't want to eat, but I've had many who ate, munched hay and chewed their cud through the whole ordeal.
Pushing: When they start pushing, you need to watch the time. Don't let hours lapse in this phase. Usually when they really start pushing, they will break a water sack, but sometimes kid, water and all appears first. A normal presentation is 2 front feet, nose will be following on top of front legs. They can kid with one leg back, and hind feet first, but if this is your first kidding and you suspect a malpresentation, get help ASAP.