brush with a good whitening toothpaste twice a day, i recommend arm & hammer brand, floss & use a good mouthwash, i recommend listerine brand. If you want to whiten your teeth fast, try crest whitestrips they work very well, although you may have some sensitivity while using them.
milk, yogurt, cottage cheese, cheese, and even icecream in moderation : ). Just try to pick foods that are rich in calcium. They will strengthen the enamel of your teeth and keep your teeth healthier.
Dairy and crunchy stuff like carrots. I had a chip in my tooth and I am a cheese-a-holic. After about 6 months the chip was gone. My dentist told me this was impossable but it happened to me. I was there as it grew not him.