There are several things that a patient can do to prevent a stroke.
First and foremost, make sure that you are following up with your primary doctor to ensure that all of your possible stroke risk factors are treated. If you have been prescribed medications (such as blood thinners, blood pressure medications, cholesterol medications, and medications for diabetes), take them faithfully.
You can also make sure you are exercising regularly and eating a balanced and healthy diet - one that is low in saturated fats/cholesterol. Other stroke risk factors include habits such as smoking and excessive alcohol intake, so if these apply to you - take action.