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.