Take a Long Leave. Okay, it's easier said than done. But the truth is that the longer your maternity leave, the longer you have to establish your milk supply and get into a good rhythm of breastfeeding. Every additional week helps, so ask for what you and your baby really need. You can always make the argument to your supervisor that a longer leave now will mean fewer days home with a sick child later.
Work that Pump. Milk production is a wonderful self-reinforcing cycle. The more your baby drinks, the more your body creates. So when your baby is in child care and you are at work, your breast pump depletes your milk supply in order to stimulate your body to produce more milk. Sadly, most breast pumps aren't as efficient as a baby, so you'll likely get less milk than you need to feed your baby. Fortunately, there a slew of tricks for pumping to boost your supply. Experiment with different methods to see what works best for you. And remember that federal law protects your right to take breaks from work to pump breast milk.
Consider Reverse Cycling. Some working mothers swear by so-called reverse cycling, in which a baby nurses more at night to make up for being away from mom during the day. For me, my sleep was more precious than even getting more mama's milk to my infant. But it depends on your body and production -- you might find it works for you and your child.
Take Care of Yourself. In fact, I found that the more stressed I got over pumping enough milk (or other stress-inducing issues), the less I produced. When I got rest and ate well, I was a fountain of milk. So remember to take care of yourself when you're a nursing mom. It takes a lot of energy to breastfeed -- anything that can wait a month or two should just wait.