Breastfeeding - How do I prepare expressed breast milk for a feeding?

First prepare clean bottles and commercial nipples.

Thaw frozen milk in the refrigerator and keep it there until you're ready for it. Do not use a microwave to thaw or warm frozen expressed milk. The milk can contain hot spots that can harm your baby. Also, the quality of the milk may suffer if it boils.
When it's time for feeding, put the thawed milk into a feeding bottle. You may want to warm up the milk again by placing the bottle of expressed milk into a container of warm water before the actual feeding.
Shake the bottle of thawed expressed breast milk well to mix any separated layers.
After each feeding, throw away any leftover milk.

Braestfeeding - How should expressed breast milk be stored?

Expressed breast milk should be kept in a sterilized glass bottle or plastic container with the date marked on it. Plastic polyethylene bags, such as commercial bottle liners, are not recommended. Breast milk contains essential antibodies (IgA) that help protect your baby. Using plastic bags to freeze expressed breast milk could cause some of these antibodies to be lost.

Store expressed breast milk in the refrigerator for up to 48 hours. You can also store it for two weeks in your refrigerator freezer (not in the door) or for up to six months in a a deep freezer with a temperature below -18°C.

When you are freezing breast milk, do not add warm expressed milk to milk that has been already chilled or frozen. This may encourage bacteria to grow.