Hi sir....   Teeth discolouration  is due to so many cause... 1. soft and hard deposits(plaque and calculus) 2.Flurosis 3.stains from tea,coffee,fold beverages... 4.Tobacco stains.. Treatment : For plaque,calculus,Tobacco stais,beverages stains, scaling(cleaning)  should be done... For mild flurosis, beaching should be done.... Eventhough you brush twice daily yhere is always some inaccessible areas that need sto be cleaned(scaling) by dentist

Post some photos. There are a number of causes for discolouration. Treatment planning is done after the cause is ascertained. Some treatment options are Tooth Cleaning by a dentist, Teeth bleaching, Laminates/Veneers.

Firstly get scaling and polishing done. That takes care of any superficial staining. Then if you still feel you want a lighter shade then you can opt for bleaching. Talk to your dentist about Home bleaching or in office bleach