What breed do you have, and how old is the dog? Do you have a quiet whelping area, away from other pets and children.If this is your dog's first litter, this is of utmost importance. Is your dog trying to make a nest,or is she following you around everywhere she can?Is the discharge clear, or tinged with blood? Does your dog seem to be restless, and is she panting? If you feel her stomach for a few minutes, and you feel any hardening, those are contractions.Have you taken her temperature at all? Do you have a puppy count from the vet (x-ray). Keep us posted.
They also start to tremble a little while they are layed down and most usually dig, dig, dig and did I mention dig? They usually pant, but I have one that doesnt so not a reliable indicator with her. Tempature is also pretty good too, will generally be 99.0 or below but have seen them whelp at higher temps.
In all, I have never had one whelp who did not act like she was shivering.