Teeth whitening strips are the most used way of teeth whitening at global way.
It's one unit consist of two strips, one for the upper jaw and second for the lower one. You have to make it stick to your teeth for some time. During this sticking period, the chemical that is tagged with the strips will soften the teeth stains. The soften teeth stains can later one be easily removed by brushing.
I would suggest to purchase teeth whitening strips. The precautions needed are,
1. Make it sure that they are recommended by the American Dental Association.
2. Use it exactly the same way as mentioned on the packaging.