What can prevent herniated disc?

Core Exercises. Typically core strengthening exercises are the best to help relieve pressure and forces in the spine. I would try and google some or look them up on youtube to see descriptions. If you can do them yourself, wonderful otherwise ask your doctor to get a referral to a good physical therapist for further assistance.
Proper lifting. One can minimize their risk of a herniated disc by always lifting properly (bending the knees, keeping the back straight, and keeping the object close to the body), and by keeping the back strong. See my health guide on back strengthening exercises.