Teeth discoloration occur due to stains (tea/coffee and many more reasons), plaque or tarter (calculus) deposition. It wont go with normal brushing, you need to visit a dentist & get oral prophylaxis done (scaling/cleaning of teeth), then you can maintain it with routine brushing habits (2 times a day) and flossing.
If natural hue of your teeth is yellowish then it wont go with oral prophylaxis.
Next Steps
Visit your Dentist and get oral prophylaxis done.
Health Tips
Visit dentist in every 6-8 months.