There are several ways to whiten teeth, including natural remedies and over-the-counter products. Here are some of the most effective methods:

1. Tooth-whitening strips: These are thin strips coated with a peroxide-based whitening gel that you wear for a few minutes daily for a week or more. Results are visible in just a few days and last at least a year.

2. Brushing with baking soda and hydrogen peroxide paste: Mix one tablespoon of baking soda and two tablespoons of hydrogen peroxide to make a paste. Use this paste to brush your teeth regularly. Use this paste daily, and you’ll eventually start to see the difference.

3. Oil pulling: Swish one tablespoon of oil like sesame, coconut, or sunflower around your mouth for 15 to 20 minutes a day. This process can help remove stains and whiten teeth.

4. Eating fruits and vegetables: Fruits and vegetables are natural stain removers as they can increase the mouth’s saliva production, which will help keep teeth clean. Strawberries contain malic acid, which is a substance that’s capable of both whitening a person’s teeth and removing surface stains that can discolor a person’s teeth. Crunchy fruits and vegetables like carrots and celery can also act as a type of scrubbing agent that will help remove stains.

5. Avoiding substances that stain teeth: Eliminating foods and beverages that contain tannins, such as wine and tea, can prevent further staining. Coffee, dark sodas, and juices can also stain teeth.

6. Regular brushing: Brush your teeth at least twice daily, and even better, brush after every meal and snack.

Its important to note that some of these methods may cause temporary side effects like tooth sensitivity or gum irritation. Also, intrinsic stains caused by the tooth itself being discolored may not be treatable with these methods. If you have intrinsic stains or are unsure about which method to use, its best to consult a dentist.