Take every medication, both prescription and non-prescription, to every doctors visit and discuss each in detail.
Ask your physician to inform you fully about each prescription and ask how it may affect other medications you are taking.
Insist that your physician and pharmacist inform you about what to expect when you take the medicine. Take notes.
Make certain you can read your physicians written prescription and ask for written material about the medicine.
Insist that your pharmacist keep a computerized record of all of your prescriptions and give you written information including a list of interactions with other medicines or foods.