How can i make my teeth whiter?

This may sound unbelievably simple, but it has worked for my daughter, our whole family in fact. My daughter's (she's 12) teeth had begun to look a little yellow. I think she was wearing the enamel away because she's fanatical about brushing, and had been doing it too long and hard for several years. Anyway, I bought a tube of the new Colgate Luminous Enamel Strengthening toothpaste. There was a noticeable difference after only three weeks! We are still on that first tube of toothpaste, and will keep buying it.