A good oral hygiene keep away all stains from your teeth. But, You need to learn brushing and flossing tips to save your teeth from black and yellow stains. Dark stains in teeth can be signs of a more serious matter such as a dead root or internal rotting. Its important to visit dentist every 6 months. Clean your teeth once a week with baking soda and salt. Use of teeth whiting strips also helps to remove black stains its not a one time process you will have to keep this process in your daily routine then it will help you.