Sometimes there are reasons you may need a breast pump to help establish milk supply. When my daughter was born she was taken to the NICU and we did not get off to a good breastfeeding start. You can read more about this here. 
I was given a hospital grade pump and told to pump after every nursing session to get my supply established.
You may need to do this due to a preterm baby, latch issues, baby in the NICU, twins or multiples or any reason that your baby does not take off nursing immediately after birth.
Here are some tips and what to expect in this situation
These are based on my experiences and what I learned while pumping to establish my milk supply. It’s going to be different for everyone so if you are in this situation please make sure to consult with a lactation consultant as well.
Try to start pumping as soon as possible in the hours after birth.
Double pump with a hospital grade pump 8-10 times a day per 24 hour period.
Pump for at least 10-15 minutes in the first few days. If you are nursing your baby as well pump after your nursing session.
In the first few days you will only see drops of Colostrum. This is great though and save those to feed your baby. I had to use a tiny syringe to do it.
After 3-4 days you should start to see more milk
Once your milk comes in increase your pumping time to 20 minutes or more. I also have heard to try pumping past the last drops of milk for a couple of minutes to increase supply. It is important during this time to try and drain your breast of milk. The more you drain the more that will be produced. Continue to pump at least 8-10 times a day. After the first seven days you should be pumping about 25 ounces or more.
After a week to ten days
By now your milk has come in and your supply should be getting established. Depending on whether you are also breastfeeding you may be able to cut back on pumping.
If you are not breastfeeding or it is not going well continue pumping at least 6-8 times a day once your supply is established. Make sure you do not go too many hours between pumping and continue to pump overnight if needed.
In my situation I reached my full milk production after a week and we were doing much better with breastfeeding by then. After speaking with a lactation consultant I cut back on my pumping. I ended up having an over supply after all my pumping and nursing for the first week and wasn’t sure how full my breasts should be once I cut back. One tip the lactation consultant gave me was that if my breasts felt hard like my forehead to continue to pump off a couple of ounces after each nursing session. If it felt softer like my nose I was probably okay to drop the pumping.
Eventually I stopped pumping except for one session in the morning right after breastfeeding. I continued to do this for awhile to build up a stash of milk. Overnight or morning is usually when it’s easiest to pump the most milk.
Tips to help increase your supply 
Lots of skin to skin time with your baby. Skin to skin has tons of benefits to you and baby.
Use a hospital grade pump. Even though I had my own pump I had already bought, the hospital hooked me up with a rental for the first two weeks. These can make a huge difference in establishing supply.
Make sure you are pumping enough times a day and for long enough as recommended above.
I don’t have much experience with herbs or medications for low supply but I know they have been very helpful for some women. You may want to ask your Dr. about those if needed.
My personal experience with this was very stressful at first but definitely worth it. I went on to have a great breastfeeding relationship with my daughter. Please let me know if you have any questions or feedback. Thank you!
Curt
August 27, 2014 at 11:45 pmNice post, my girlfriend would like it , i will share it with other on my social media.
Jen
August 28, 2014 at 7:48 amHi Curt! Thank you!
Intha
October 30, 2016 at 2:38 pmThank you for sharing Jen. Yes the theory is to pump after each feed, but even with my second child i havent mastered it yet. I do believe that my milk supply is enough (for direct breatfeed), but i always have this feeling that it wont be enough if i pump as well. The issue is that i am a working mom, and both my daughters are loved being carried, they hate the flat surface and will immediately cry soon after being put down. I REALLY want to stock my milk supply for my second child (she’s 2 months now and i will be back to work in 1 month), do you have any tips for me? One more issue is that she couldn’t have a perfect latch but my doctor said it was fine since her weight is enough, but i worried that the breast isn’t fully emptied so that the milk would not reload as fast as it should be. I wonder if you know how fast does the milk reload after each feed/pump?
Thank you 🙂
Jen
October 31, 2016 at 12:04 pmHi,
Take a look at this page, especially the last part about breastmilk refilling and hopefully this will help you understand how it works. You can’t feed or pump too often and deplete breastmilk, more will continue to be made. I recommend still attempting to pump after a feeding, maybe the first one in the morning, if you want to try and build a stash up before you return to work. I know it’s hard to work around our kids needs, I find it hard to find time to fit in pumping myself. Here is the link, I hope it helps!
http://kellymom.com/bf/got-milk/basics/milkproduction-faq/