The primary effect of aileron deflection is roll. The secondary effect is yaw, and it is this yaw that can cause problems with tracking in rolling manoeuvres. How is it minimised, or better still, eliminated?

It is the down-going aileron that causes the problem. While increasing lift on that portion of  the wing it increases induced drag, yawing the plane in that direction, usually the wrong direction which is why it is called adverse yaw. So it would seem that decreasing movement in the down-going aileron relative to that of the up-going one would be the solution. Aileron differential - more up than down, usually. (Fig.3)

Modern computer radios have the facility to adjust differential electronically, but it is possible to achieve the same result mechanically using the rotary output of servo arms.
 
 

Both these arrangements will produce differential movement of the pushrods. The relative lengths of the arrows shows the direction and magnitude of the differential.

The set up shown  in Fig. 1 would suit high wing trainers and low wing planes with aileron servos installed outboard in the wings. Fig. 2 shows the set up for low wing planes with one aileron servo sitting upright in the centre section.