When a newborn infant begins to cry, the adult should?

The parent should think about what the baby might need. When babies cry it's because they need something, or they're upset. Sometimes they'll cry because they need their diaper changed, or they are hungry, or sometimes they'll cry because they want attention, or they're scared.
Babies cry easily because after being in the womb, even the slightest discomfort is the worst they've ever felt.