Stay out of sight
From birth to about 15-18 months, a baby can be taught to sleep
in a crib.
After 15-18 months, some babies can climb out of a crib. From the beginning, parents should keep a consistent, unexciting bedtime routine, so their baby gets sleepy instead of stimulated. After putting the baby down to sleep, parents should stay where the baby cannot see them, if their baby is a hard-to-fall-asleep baby.