The body's posture - For a wrist device, the elbow should be bent slightly and the monitor held at chest-height (same level as the heart). For upper arm devices the arm should be relaxed and placed on the table.
The environment - Stress will make blood pressure rise so ensure that the "measuring" situation is as relaxed as possible. Ambulatory blood pressure monitoring provides a more reliable measure of a patient's blood pressure, as patients don't experience the 'white-coat effect', which can overestimate readings, particularly in susceptible patients. However, clinical measurement of blood pressure is useful for screening and in the management of suspected and true hypertension.