1. Brush your mouth properly
Yes, your mouth, not teeth. The reason is that your teeth is not the only thing in your mouth; you have your gum, your tongue and the roof of your mouth. Those need cleaning too. Also, make a habit of brushing at least twice a day, preferably in the morning and in the evening.
2. Floss regularly
As wonderful as brushing regularly is, it is not holistic in its responsibility to clean your teeth. Brushing can clean the surface of the teeth, but it cannot do the same for the spaces in between teeth.
3. Limit intake of sodas and alcohol
Tobacco for one, is something you should run away from. Avoiding this can save you from some periodontal complications such as oral cancer. Furthermore, stuff that you will take to mask the smell of tobacco such as sweets, tea or coffee will just end of doubling the damage to your teeth already caused by the tobacco.