The most common reasons to pump are to collect your milk so your baby can have it when you're not around and to maintain your milk supply for when you're together. This is important if you're going back to work but want to continue nursing.

To get the hang of it, it's a good idea to practice pumping for a few weeks before you need to rely on expressed breast milk for your baby. Just make sure that breastfeeding is well established before you give your baby the bottle.

Pumping also means you don't have to be on call for every feeding when you're at home. Your partner (or another helper) can feed your baby your milk from a bottle, allowing you to get more uninterrupted sleep or take a break from baby care. (Letting Dad take over some of the feedings also helps him bond with the baby!)

You can also use a breast pump for these reasons:

Most women express their milk using an electric or manual pump. Some women prefer to express their milk by hand, but most feel that using a pump is faster and easier.

Although it may feel strange at first to use a machine to get milk from your breasts, it usually doesn't take long for the process to become quick and easy.

To use an electric pump, you put a breast phalange (or shield) over your nipple, turn the machine on, and let it do the work of suctioning your milk into an attached container. (Phalanges are supplied with the pump.) Manual pumps also use a phalange, but you extract the milk by operating a squeeze mechanism or pulling a plunger with your hand rather than relying on a motor.

It usually takes ten to 15 minutes to pump both breasts with a good electric pump and up to 45 minutes with a hand pump.

Good breast pumps mimic the sucking action of a baby and won't cause you pain. Be sure to use the right size phalanges for your nipples and position them just right so you don't pinch or irritate yourself.

Consider buying a hands-free pumping bra so you don't have to hold the phalanges on your breasts. (That way, your hands are free to hold a book or magazine, type, or dial a phone, so you can read or work while you're pumping.) Some moms make their own pumping bras by attaching rubber bands to the clasps of a regular nursing bra or cutting holes in an old jogging bra.

Remember that for best letdown and milk production, you'll need to be calm and relaxed.

Initially you'll feel quite a tug from a fully automatic pump. Start with the lowest level of suction, then turn it up as needed once you get going. It shouldn't hurt, but it may feel a bit odd. Remember to clean the pump parts carefully after each session.

Choosing the breast pump that's right for you depends on how often you plan to use it and how much time you can devote to pumping. If you work full time and have to find time to pump during a busy workday, you'll want to use a fully automatic pump so you can pump both breasts quickly at the same time. But if you only need to pump a few ounces occasionally, an inexpensive manual pump may do just fine.

If you only need to express milk every once in a while – say, for a rare bottle-feeding – you may be able to get by with expressing by hand, although it might take a bit of practice to get it down.

Hand expressing a little breast milk can help soothe engorgement and plugged ducts. And if you have sore, cracked nipples, you might want to express a bit of breast milk by hand after each nursing session to rub over them and soothe them.

Many women find that expressing milk by hand is time-consuming, though, so it isn't usually feasible if you need to express a larger amount of milk regularly.

It helps to have someone demonstrate this for you, but here's a step-by-step:

You can store breast milk in a feeding or storage bottle that's made of plastic or glass. A secure cap will keep it fresh. (Many pumps come with storage containers.)

You can also use a plastic bag made especially for storing milk. Fill the container three-quarters full if it's going in the freezer, to allow for expansion.

For convenience, store the milk in the amounts that you normally use at a feeding. (If your baby typically takes 3 ounces, then store in 3-ounce portions.)

Remember to write the date on the bottle or bag before putting it in the refrigerator or freezerso you'll know when you pumped it. (You'll want to use the oldest milk first.) Don't combine fresh milk and frozen milk (by topping off a frozen container with some fresh milk, for example).

You may be surprised to see what breast milk looks like. It's normal for the fat to separate and float to the top, and sometimes the milk has a bluish hue, especially early on. (Your milk color may also be affected by your diet or medications.) Don't shake the milk. Instead, gently swirl it to mix the fat back in.

Your milk shouldn't smell or taste sour, but after thawing milk sometimes has a slightly soapy smell from the change in the fats. This is perfectly fine.

The process of freezing destroys some of the antibodies in the milk, so don't freeze it unless you have to. But frozen breast milk is still healthier and offers more protection from disease than formula does.

There are different opinions on how long breast milk stays fresh once it's left your body.

(Use the lower numbers – three months and six months – for best quality. At the higher end, the milk is still safe, but the quality will be a bit lower.)

Once you've thawed frozen milk, you can keep it in the refrigerator for up to 24 hours. If it's at room temperature, use it within one hour. (If you haven't used it in that time, you'll have to throw it away, since you can't refreeze it.) If you need to transport milk, keep it cold until just before using.

Some health professionals recommend throwing out any milk that's left in your baby's bottle after a feeding, though others may tell you it's okay to save a bottle of partially consumed breast milk as long as you refrigerate it right away and use it within four hours.

To thaw frozen milk, hold the bag or bottle under warm water until it's a comfortable temperature or let it defrost in the refrigerator overnight. Don't use the microwave for defrosting or warming, because it kills the nutrients in breast milk and hot spots can develop.

For many women, the most difficult thing about pumping is finding the time to fit it into their schedule during the workday or finding a comfortable, private space to do it in. But pumping doesn't come easily for everyone. Here are some reasons you may be having trouble getting much milk out and some tips for what to do about it:

Many breast pump companies now make breast phalanges in larger sizes. Make sure you're using the size that's right for you.

If you're having trouble or feeling discouraged, call a lactation consultant. Or talk to pumping moms in our Community. They can help and be a great source of support.

Top tips from moms who pump

Video: How to use a breast pump

Breastfeeding and pumping while traveling

Breastfeeding and the working mom

BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

ABM. 2010. Protocol #8: Human milk storage information for home use for healthy full-term infants. Academy of Breastfeeding Medicine. http://www.bfmed.org/Media/Files/Protocols/Protocol%208%20-%20English%20revised%202010.pdf [Accessed April 2016]

CDC. 2010. Proper handling and storage of human milk. U.S. Centers for Disease Control and Prevention. http://www.cdc.gov/breastfeeding/recommendations/handling_breastmilk.htm

FamilyDoctor.org. 2005. Breastfeeding: How to pump and store your breast milk. http://familydoctor.org/online/famdocen/home/women/pregnancy/birth/828.html

La Leche League International. Undated. Common concerns when storing human milk. http://www.llli.org/NB/NBJulAug98p109.html

La Leche League International. Undated. What are the LLLI guidelines for storing my pumped milk?

Mayo Clinic. Undated. Breast-feeding: 7 tips for pumping success. http://www.mayoclinic.com/health/breast-feeding/FL00120

OWH. Undated. Pumping and storage. U.S. Office on Women’s Health.

Sutter Health. Undated. Expressing and storing breast milk. http://babies.sutterhealth.org/breastfeeding/bf_expressing_storing.html

Stanford Medicine. Undated. How to hand express milk. http://newborns.stanford.edu/Breastfeeding/HandExpression.html

What to Expect. Undated. Pumping breast milk 101. http://www.whattoexpect.com/pumping-breast-milk.aspx

Jenny Des Jarlais is the associate director of digital content strategy at the University of California, San Francisco. Previously, she was a senior editor and managing editor at BabyCenter, as well as a health researcher, writer, and editor.

Des Jarlais lives in Oakland with her husband and two children.