How much over my normal blood pressure should i start the measurement from it's my pressure is normally 120 over 80 what should i pump up the cuff - to start to get a reading?

Yes: If normally you get the reading of 120/80, you should pump up the pressure to 160 or so and gradually come down to appreciate the change in sound indicating systolic and diastolic limits. But if you are normal, without significant risk factors , you need to monitor not more than ever few weeks or once a month. Feel good!

Normal: Approximately 150. 20 to 30 mmHg over normal

180mmHg: I would inflate the cuff pressure to 180mmHg and slowly dial it down from there. That way, you will be able to catch if your blood pressure may be elevated on occasion. Remember, blood pressure changes regularly throughout the day and is not a stagnant number.

20points above: Cuff should inflate to 20pts above systolic number. As a safe bet inflate to 200mmhg. Other option is if you know how to check radial pulse then inflate to 20pt over when the radial pulse dissappears as the cuff is inflating.