Brush and FLOSS twice a day : As repetitive as it may sound, these are two things that work. Most of us brush once a day and don't floss at all. These lead to a build-up of stains on teeth. If you do these two things properly, you may never need a dentist ever.
Coffee and Tea Intake : Limit the frequency, shorten the time you take to drink these beverages and use straws whenever possible.
Wear splints for grinding: Grinding causes the wearing away of teeth making them look yellower apart from numerous other bad effects on teeth, joints and muscles. Wearing a splint prevents all these negative effects of grinding and clenching
Don't ignore chronic vomiting and stomach acidity : Long-term exposure of teeth to acids causes the topmost white layer to erode leading to the teeth looking yellow
Use a remineralizing toothpaste or tooth creme daily : Remineralizing products contain fluoride, nanohydroxyapatite or amorphous calcium phosphate and reverse effects of acid attack on teeth leaving them looking shiny and white