Here is a good resource: Average Growth Patterns of Breast Fed Babies
And a fabulous article entitled: How much expressed milk will my baby need?
I did not start pumping until four weeks after delivery and initially tried to pump after feeding twice a day, as was suggested by my lactation consultant. After several frustrating weeks of getting out a few measly drops of milk per session, I started pumping between feedings and especially pumped if my son took an extra long nap or if I skipped a feeding and we gave a bottle. This worked much better for me and I was able to get out 2-3 oz at a time. As I work from home, I was able to primarily breast feed so I never developed a great pumping schedule or a large freezer supply.
This is a nice post, Pumping Schedule from NB to 12 months, about pumping while breastfeeding and also about exclusively pumping.
If you're having difficulties, seek out lactation resources! Your maternity center at the hospital or your pediatrician's office can advise you!
Useful items if you plan to pump breast milk:
Breast Pump. Every resource I read agreed, and I concur, a double electric pump is best. Hand pumps are useful for car trips or if you anticipate not have access to an outlet, but many electric pumps also come with a car or other power source adapter these days. The electric pump will provide the best suction. The double allows you to pump both sides simultaneously, thereby taking half the time than if you were to do each side individually. I've heard of people pumping one side while baby eats off the other - they must be more coordinated than I am! - and in that case a single pump could be useful.
Choosing a pump is a tricky business. There are high and low reviews for them all. Testimonials can be found on every brand raving about one pump being so much faster than another, getting out so much more milk, etc. If your insurance will reimburse you for the cost of a pump, make sure to contact them and find out what products they will cover. I purchased the Medela Pump in Style Advanced Pump with On the Go Tote which is a popular choice.
Nipple Shields. Believe it or not, the size of nipple shield you need has nothing to do with the size of your breast! It has to do with the diameter of your nipples. You can purchase online or in store from your pump manufacturer, from a 3rd party such as the Pumpin' Pal, or obtain from a lactation consultant. At my lactation visit in my pediatrician's office, the consultant supplied me with the proper size shield. Most pumps come with a size Medium - 24 mm. If the shield you are using is too small you will get friction. Friction leads to pain...enough said.
Nipple Balm. I liked the Honest Co.'s Organic Nipple Balm. It has no real smell or color to it, is all organic, and doesn't need to be wiped off prior to feeding. Any balm which does not need to be wiped off prior to feeding will work though. I would try pumping without applying balm first, but if needed you can apply the balm prior to pumping to prevent sticking to the nipple shield.
Pumping Bra. This is an optional item, but if you are using a double pump you'll want some way to secure the shields other than holding them in place. Holding them is awkward and you can't adjust the pump (or do anything else!) if you are holding a shield with each hand. You can fashion a simple apparatus to hold the shields in place using your nursing bra and hair ties. Check out this Great Blog post. I found the hair tie method to work well when my milk was flowing well, but when not I preferred the tighter pumping bra which kept everything snug. I had a very simple pumping bra similar to this one which I was given by a friend - have I mentioned how much I love hand me downs?!?!
Storage Containers. Most milk storage solutions are appropriate for both refrigerator and freezer use which is very convenient! I used the Lansinoh Breastmilk Storage Bags with great success. I liked that you write on the tab above the actual bag and that the bags curve for easy pouring. I only had one ever leak when I thawed the milk - but a good idea is to thaw your milk bag(s) sitting in a clean container so you can still use the milk if a bag does leak once thawed. There are many other similar brands on the market. I also had a dozen of these Medela 2 oz Breastmilk Containers. I pumped into these most of the time because I seldom got out more than 2 oz per side at a pumping session. I found them easier to handle than the larger 5 oz containers which came with my pump. Your pump should come with several pumping and/or storage containers.
Bottles. If you are exclusively feeding breast milk, you will not need 8 oz bottles. Only formula fed babies ever eat that many ounces at a time. I didn't know this and registered (and received!) a nice package of 8 oz glass bottles which I never opened. Because I didn't give many bottles and really never gave two bottles in a row, I only ever used two 4 oz glass bottles. I used Dr. Browns Glass Bottles which do not seem to be available any longer! The new product is Dr. Browns Wide Neck Glass Bottle 5 oz. I also used Dr. Browns Preemie (stage 0) nipple for the first 4 months which is the slowest flow stage you can buy. My son never spit up or choked with the stage 0 nipple, but after a while my husband observed it was taking him longer to bottle feed than it took me to breast feed(!) and we advance to the stage 1 nipple which my son used up through his final bottle feeding at around 10 months old. For plastic bottles, the Philips AVENT are a popular brand.
Microwave Sterilizer. Pump parts and bottles should always be washed in hot water with dish soap - I like 7th Generation brand dish soap. Some items can also be run through the dishwasher. Either way, the periodic use of a sterilizer, or sterilizing in boiling water, is recommended. I used the boiling water technique - all you need is a big stock pot - until I was given (hand me down!) the Philips AVENT Microwave Steam Sterilizer. You add some water, load in your bottles, nipples, and pump parts, and pop it in the microwave for 6-8 minutes (depending on microwave strength). I've also heard good reviews about Microwave Steam Bags.
Drying Rack. A clean dishtowel would do, but it's nice to have something that holds all the little parts and allows for air flow. If you have the counter space, how cute is the Boon Grass Countertop Drying Rack??? Also has flower and twig accessories!
I didn't have this product, but friends of mine liked theirs. I received a hand me down rack Similar to This which was more than adequate and I would recommend as it holds a lot of items for drying at once.
I think that is everything! If I missed an essential supply, please let me know!