1. Brush your teeth with baking soda, just a little goes a long way. Wet your brush a bit then takes some baking soda on the brush like toothpaste. If you hate the taste you can brush your teeth with real toothpaste afterword. it really work made your breath smell fresh too and it cheap!
2. Using hydrogen peroxide as a rinse before brushing, it may burns a little. It doesn't taste great, don't swallow it. Or you can put Hydrogen Peroxide on with Q-tips.
Careful with the peroxide, you could damage your gums & teeth. Don't use the peroxide to often.
3. Hydrogen peroxide and baking soda mixture. Apply to surface of teeth, leave on half an hour, rinse off if gums start to sting then use your toothbrush to really make it work. It is too abrasive to do every day. Use this method no more then 1 or twice a week. Beware do not swallow it.
4. Whitening tooth kit which you can found easily in most chemists, make sure to follow instructions carefully cause it's easy to screw up.
5. Teeth whitening toothpaste or Gel. Use it regularly, you will notice a difference. Whitening toothpastes remove surface stains and prevent new stains from building up. However they are not in contact with the teeth long enough to remove internal stains.
6. Try a Sonicare toothbrush, by the powerful oscillating or rotating movement brush can actually make it easier to clean stains. Like you brush 3 times more when compare to normal brushes.
White teeth are not a overnight miracle. You should prevent your teeth from stains and always white easily by just brush your teeth really well twice a day and stop eating / drinking things like coffee, tea, carbonated drinks or smoke. It 's also keep your oral heathly from other problems.