
Try not to have unrealistic expectations. Not everyone will have a nice white smile. Keep in mind that if you smoke the results may take longer and then may not last as long unless you refrain from smoking. Also keep in mind that the natural whiteness of person's teeth is about the same as the whiteness of their eyes. People who have blue gray staining of their teeth should know it will take longer to whiten, maybe up to six months of home treatment and visits to the dentist. People with dark stains may have better luck with veneers, bonding or crowns.
There are some side effects when whitening your teeth. One of them is temporary tooth sensitivity and some irritation of the gum or soft tissue in the mouth. The sensitivity usually happens in the first couple of days of the bleaching process. However the conditions usually disappear after a few days.
I've used a product called Denta White and the results have been exceptional. What I did was use their free trial about 9 months ago and it worked nicely so I bought one of their kits a few weeks later and my teeth turned about 8 shades whiter. What I do is use some white strips, like one a week and my teeth still shine.
Heres a link to Denta White... Hope you have great results.
Click here for Denta White