Are there proven ways to help prevent bell's palsy?

No. There is no definite way to prevent bell's palsy as the exact cause is unknown. Although it may be caused by a virus, there is no vaccine or other known prevention.
No. Bell's palsy has multiple possible causes, including ENT infections, lyme disease, herpes and others. There is no way to predict your acquisition of these causes and therefore no means of preventing its development, but this is not a very common illness.
Bells palsy, stroke. Bell's palsy, a weakness involving one side of the face and of viral cause and specifically not a vascular event such as a stroke, can not be prevented any more than the common cold. Keeping your self fit and thus boosting your natural immunity and good diet are the best defense and treatment. Management of symptoms and their cause, seek an eye care specilist's help.