Fruits,vegies, EFA's. You are what you eat so healthy foods create healthy skin. Essential fatty acids from salmon, sardines, flax oil; antioxidants from berries/cherries, selenium from brazil nuts, zinc from nuts, seeds & dark chocolate and green tea are among the better foods for skin; avoid fried & processed foods, hydrogenated oils. See this: http://www.Webmd.Com/healthy-beauty/features/abcs-of-healthy-skin-diet.
Well balanced diet. Magazines are full of lists of foods that are "good for your skin". Notice that these articles are never written by dermatologists, or anyone else that actually knows anything about skin. Eat a well balanced diet and your skin will do just fine.