Rinse out your mouth with one percent hydrogen peroxide. Hydrogen peroxide strips are expensive to buy and harsh on your teeth. Keep the peroxide in your mouth for at least a minute and make sure you do not swallow an excessive amount of the solution. Follow up by brushing your teeth.
Avoid using mouthwashes that contain alcohol or have coloring added to them. These colorings are known to have a staining effect on your teeth. The chemicals that they use are also not good for you. One well known mouthwash has been known to stain your teeth a brownish color.