The best thing that you can do for your teeth is to brush and floss them daily. You should brush at least twice daily and floss once per day. It would help if you used a quality toothbrush and toothpaste. Be sure to also brush your tongue because bacteria can collect on it as well.
Another thing that will help maintain your dental health is by improving your diet. Try to avoid foods that are high in sugar. If you are a smoker, quitting will do wonders for your oral health.