How often should I get my blood pressure checked?

I recently had to put together a family health history report for a class and learned that high blood pressure and high cholesterol has been a common condition throughout my family. I know my dad has high blood pressure and is currently on medication for it (not sure what he takes).

I had blood work done about 3 years ago and was told my blood pressure was a little high, but not significant enough for further treatment. I was told to simply cut back on the fast food, which I have done. But when should I get checked again? And how often should you have your blood pressure checked?