My supply took a big hit after I started working again.  Here’s what worked for me (thank you to all my friends at My Mommy Time who helped me with this!):

-Drink a ton of water. This is by far the most helpful. I drink about 100 ounces a day.
-Eat old fashioned oatmeal.  I make a big batch every Sunday and it keeps until Friday.
-Add flax seed meal to foods. I put it in my oatmeal every morning.
–Brewer’s Yeast (a supplement that can be found at GNC or Whole Foods) **Brewer’s Yeast is different than active or dry yeast** I also add a bit of this to my oatmeal every morning.
–Fenugreek (a supplement that can be found at GNC or Whole Foods)
-Blessed Thistle (a supplement that can be found at GNC or Whole Foods)
-I took a supplement called More Milk Plus that has Fenugreek, Blessed Thistle, Nettle Leaf, and Fennel Seed. The capsules are WAY better than the tincture. Expensive but worth it!
–Pumping for 10 minutes AFTER you stop dripping milk. If pumping while away from your LO you should pump for 5 minutes after milk stops dripping to maintain your supply. I pump for at least 20 minutes at a time while at work. If you don’t have it already, invest in a good handsfree pumping bra.
–Lactation cookies!! The active ingredients are the oatmeal, flax seed meal, and brewers yeast. I substituted coconut butter and applesauce for the butter-YUM. Only problem is I can’t stop eating them so I just add the elements to my oatmeal so that I don’t get HUGE.
–Try not to stress. I found that stress is the number one issue with my milk supply. I make sure to do something that isn’t stressful when I’m pumping (like write posts-HA!). If I work I don’t get nearly as much milk.
–Nurse as much as possible. I nurse Lucy as soon as I get home. Then right before bed. During the weekend nurse, nurse, and nurse and try to throw in one pump session a day.

I hope this helps!