This article explains a lot about what is needed to help little ones survive:
http://www.showpapillons.com/formula.htm
I always do the same as JeanieK but if they can't latch on you have to take immediate action. Sometimes they can't latch on because of a cleft palate or because the mom's teats are too big or the pup is too weak. I have found that the glucose solution really helps to get them going if they are just weak from expending their glucose levels. Sometimes pups are just not fully developed or have internal problems and in those cases there is nothing that can be done to save them.