Make sure there is always fresh milkweed leaves and change the water daily. (I have found best method for Common Milkweed is to cut stem, put in water and refresh the water again after the "milk" stops flowing.)
Clean area of caterpillar droppings (fresh paper towel) daily.
Fascinating changes kids can observe raising butterflies:
(3-5 days) Egg turning black - caterpillar hatching
(4 times) Caterpillar is still for a long time - sheds its skin and eats it!
(10-14 days) Caterpillar spinning button of silk - attaches its rear - swings into "J" position
(less than 24 hours) caterpillar antennae becomes limp, caterpillar straightens and moves, skin splits - chrysalis appears!
(1-2 hours) Chrysalis dries - forms beautiful golden necklace
(9-14 days) Chrysalis turns black and transparent - Monarch wings can be seen
(less than 24 hours) Chrysalis gets slightly "cloudy" and starts to split from bottom sides - butterfly emerges!!
(1/2-1 hour) Butterfly pumps fluid into its wings - wings expand