Tooth is externally covered by either tartar or stains. These can be cleaned by general cleaning and polishing. As u have confessed of having habit please refrain from it so that not only Oral health but also general health is maintained. It's always a good habit to brush daily twice with a good foaming tooth paste and soft or ultra soft tooth brush and to visit a dentist every six months for general check up and cleaning.

hello your problem is general you probably need to brush twice a day. with a paste which is not sweet and acidic like Colgate strong teeth pls do not trust a paste which claims to whiten your teeth.its all false.pls see a dentist and get the stains caused because of your habit cleared or cleand and if you still feel yellow may be you need to get whitening of your teeth with your dentist

visit a dentist near by and undergo scaling and polishing.. later stop the habit and go for brushing twice daily with snowdent.