In order to get a perfect BP reading, one needs to do the following:
Measure the BP thrice with less than 1-minute gap between consecutive measurements.
Calculate the average of the 3 readings.
Do not wear tight clothes and do not put the cuff above the clothing
Empty your bladder before measuring the BP
Take rest for at least 5 minutes before the measurement
Keep mobile phones and electronic devices away
Do not consume tea, coffee or any caffeinated drinks before the BP measurement