Unfortunately there are no clear cut ways if you wish to prevent teeth grinding permanently.
However there are many ways which will gradually lessen the intensity and occurrence of this problem.
Depending on the cause one can choose any of these procedures to achieve results.
However your dentist is often the best person to make a correct diagnosis and prescribe a suitable treatment.
Also only a dentist can say for sure if you are suffering from teeth grinding or bruxism as it is medically called.
Some holistic methods you can use to prevent teeth grinding are to avoid alcohol, tea, coffee and anything with chocolate.
Your dentist may prescribe a night guard to prevent the contact of teeth during sleep.
If the reason is stress your dentist may recommend injections of botulinum toxin into the gums.
You could also be referred to a psychiatrist for psychotherapy.
Other good ways of treating stress induced bruxism are aversive conditioning in which the patient is woken up when he grinds teeth.
Jaw exercises work well too, examples are alternate clenching and relaxing of teeth, for 5 minutes each (this is in my opinion the cheapest as well as one of the most effective therapies available).
However if your jaws are improperly set, you may be me more anxious about how to prevent teeth grinding.
But there is no reason to worry, treatment in your case is not complicated and does not involve surgery.
The dentist will probably use occlusal therapy, this means you may be given braces, and at the same time any damage done to your teeth by grinding will be fixed (this is naturally needed with any bruxism treatment).
But always remember that the dentist is the most qualified person to prescribe exactly how to prevent teeth grinding in every particular case.