The first and foremost thing is to be aware that teeth are living parts of our body and may give rise to problems anytime in future which may start with some symptom or may be symptomless.
Regular brushing at least twice a day whether food has been eaten or not,brushing with a soft toothbrush for two minutes each time.
Flossing at least once a day,preferably at night before going to bed.
Using a mild mouthwash after brushing at night.
A visit to dentist regularly to check initial signs of tooth decay or gum disease or any other oral/mouth examination (even though teeth are not giving pain).
Making slight changes in the diet also helps. Including fresh fruits and vegetables in your diet can help to keep the body and teeth healthy in the long run.
Minimising the intake of refined and packaged food and also carbonated drinks helps prevent dental disease.
Getting a regular oral prophylaxis/scaling/cleaning done ,ideally every 6 to 8 months is important.
Fluoride application and pit and fissure sealants may also help in preventing dental decay. These are done by the dentist.
Understanding oral habits which may cause damage to the teeth unknowingly should be identified and rectified at the earliest(e.g.Night grinding or bruxism,tongue thrusting,thumb sucking etc)
Healthy diet plays an important role in prevention.