I don't think there are any foods you should avoid; but, there is a way to absorb more iron from the foods you eat.
If you are eating an iron-rich food, drink a glass of citric juice while eating it. The citric juice allows your body to absorb more iron when eaten in conjunction with citrus than when eaten without a citrus component.
Also, eat plenty of iron-rich foods that do not require cooking to avoid losing any goodness during the cooking process. For example: a spinach salad or a salad with spinach added combined with citrus is an excellent source of iron.