The most accurate way to test your blood pressure is going to your physician or doctor. For home testing, however, you can obtain fairly accurate results by using an upper arm blood pressure monitor like this one from Omron. Testing yourself can be tricky if you are not trained to do so it’s best to take your monitor in with you to the doctors office to get advice and to check for accuracy. Make sure when using a digital monitor that you remain as motionless as possible.
Wrist monitors have also been getting great reviews lately for accuracy. In fact the series 7 wrist monitor from Omron got great scores by consumer reports.
Your other alternative would be the manual aneroid blood pressure monitor but these should be reserved for professionals and individuals that have a firm grasp on how to take a reading.