What is the best way to stop a newborn from crying after she has eaten and when she wakes up from a nap?

First you must try to find out why the kid is crying. It is the only form of communication they have. Is it aloneness, pain, hunger, illness or just to use their fussing muscles to help push food along the digestive tract. They have weak flabby belly muscles that often must be assisted by their fussing. Some do more than others. If you check them out & do all you can its okay for them to just fuss