Whitening toothpaste can help reduce stains (coffee, tea, tobacco) on the outside of teeth.
But, to really whiten teeth, there are three different types of 'bleaching': 1. Over-the-counter = crest whitestrips. 2. Trays that hold bleaching gel against the teeth, and 3. In-(dental)office bleaching. All three types of whitening are effective. The faster the effects, the more expensive.