The obvious answer would be to avoid eating or drinking anything that can stain your teeth in the first place (coffee, black teas, soda, sugary foods, etc). However, since most of us need caffiene in our lives to help us function, I use Crest Whitening Strips. They work really well, even when used only once a day a couple times a week. The down fall is that they must be left on for a half-hour. I always get compliments on how white my teeth are, so I always recommend them.