Make a pumping plan

When you're away from your baby, you'll need to pump your breasts every two to three hours, depending on your baby's feeding frequency at home. If you are away from your baby for an eight-hour workday, plus commuting time, you should expect to pump about three times. Pump as long as it takes to empty both breasts. You'll see the milk flow start to slow and your breasts will deflate as they do when your baby is finished nursing. It will take about 25 minutes to set up your equipment, pump both breasts at once, and then get dressed and pack your bottles of milk.

Protect your precious cargo
It's best to store your pumped breast milk in an office refrigerator, and then carry it home in an insulated bag or cooler with an ice pack. (If you don't have a refrigerator at work, the latter will do.) At home, store the milk you pump in clean containers, labeled with the date so that your care- giver can use older milk first. Breast milk can be kept safely in the refrigerator for two to three days, and in a separate freezer unit (with its own door) of a refrigerator for three or four months. It can also be safely stored in a stand-alone deep freezer for 6 to 12 months.
Store frozen milk in serving-size amounts  -- probably 4 to 8 ounces, depending on your baby's age and size  -- so that it's quick to thaw. Defrost the milk by holding the container under warm running water, just to take the chill off. Overheating may destroy valuable nutrients, so never microwave breast milk.