They actually have an article on this site on what foods are best for breastfeeding. I don't remember If It's In the article, but I know that you should also continue to take prenatal as well.
Here's the article about It:
Yup plenty of fluids, prenatal vitamins, oatmeal is supposed to be good for boosting your milk supply. Basically healthy foods and the occasional splurge. Garlicky, spicy, onions, pizza, spaghetti MAY make baby cranky so go easy on that stuff when you can. Its also important to keep light snacks near by while nursing such as animal crackers, whole wheat crackers, pretzels etc because you will feel like you're starving since producing your own milk requires alot of your caloric intake. Good luck! Breastfeeding is a wonderful experience!
Plenty of fluids!! I kept taking my prenatal vitamins after I had my baby too.