Katie is right in some aspects. The dogs tempeture will drop to about 98.6 and labor should begin. They go thru stages of labor. Their tempature will drop and go back up for a period of time. The dog will start nesting and panting maybe heavily. She will lay down and you will be able to see contractions as she pushes the pup toward the birth canal. Then the pup will be born and mom will clean it up. She'll eat the placenta and that is necessary for her hormones. Females don't always have puppies on their scheduled due date either. They can be a week early or week late. If your dog is a small breed, you need to make sure she is carrying at least two puppies. It makes it easier for her to give birth. If it's only one puppy, it could grow too large and mom would need a c section. Good luck.
If your dog does not go into labor within twenty- four hours of her temperature dropping below 100 degrees, then you need to consult a veterinarian. You also need to make sure that the mother is alert and giving care to the puppies after they are born. If she is not then call the vet.
Also, keep in mind the dogs uterus has 2chambers, so if she had a pup or two and it looks like she is done, she isn't yet. She will rest a couple of hours Andy Hen bless you more. Do not bother the dog, just check on her periodically and do not allow children and others to bother her. Take cool water so she can drink and talk softly and gently feel her tummy and ahead of the vagina for swelling as you can tell if a puppy is on the way. Do not attempt to insert fingers in the vagina to help, but if she needs help, gently pull the baby out and rub it with terrycloth to stimulate and place it near the mommy, so she can clean it up and eat the placenta.