Ive purchased a new almost ready to fly model trifecta from hobbyking.com. I am using a kk mini board and a turnigy metal gear servo. However, I have trouble setting up the same. The tri is rolling about yaw however I change PID. Also the servo is acting strangely fluctuating before arming and not giving equal rotations on both sides......Please somebody help me out on this.....!!

Check for any play in the yaw mechanism and that arm also .

I dont understand. please explain.

Check for any unwanted looseness in the yaw mechnism

use this video to rectify yaw problem

Hey, thanks... I got through that one....I just had to reset the board and the rest is history.....
After a few good flights and then a crash, when I tried flying it again, it has become very unstable in the vertical axis(throttle) and is quite shaky.....