How to correct a drifting drone

My drone drifts to the left without any stock input. The yrims are all centered and for me to counter it I have to give it stick input to the right. What can be done about this.

I had this same problem running DJI Naza. Had to recalibrate the IMU. Problem solved.

If you are using baseflight/CleanFlight/Betaflight:
Land. Disarm. Full throttle (will not spin motors if disarmed).
Take right stick and move opposite the drift direction. Every blink on the flight controller indicates one step (about 1 per second). Just start with 3-5 blinks, and work from there. Mine flies perfect up/down now.