If you are doing it your sleep, you can get a mouth guard at your local drug store. If you are doing it while awake find some way to manage your stress. Meditation, and massages can help.
How to stop Tooth Grinding?
Take help from a periodontist.
Avoid colas, chocolate, and coffee.
Avoid alcohol.
Do not chew on pencils or pens or anything that is not food.
Train yourself not to clench or grind your teeth