If you decide to start expressing milk, be sure that you have experienced the let-down reflex which means your milk is mature. Also give yourself enough time and practice breastfeeding to be sure you are producing enough milk. This has usually happened by the end of the first month after childbirth. It is important that expressed milk be handled and stored with care. Always wash your hands and nails first, and use very clean containers to hold expressed milk.
Most pumps come with a container that is suitable for storing breast milk.
If you do not plan to use the milk within 30 minutes, it should be refrigerated. Expressed milk must always be kept cold, even when being transported. Milk that is not going to be used within 48 hours of pumping should be frozen. Let the milk chill first in the refrigerator, and then freeze it. Never combine freshly expressed milk with older milk.