Which matters should take in mind for calculation of torque and which are not?

Explanation

The role of moment of inertia and torque in the rotational motion of rigid body is similar to the role of mass and force in translational motion.
In rotational motion of rigid body only components of torque parallel to fixed axis should be taken in mind because these components are responsible for rotation of the body relative to axis.
Component of torque perpendicular to the axis of rotation, rotates the axis from its position.
For cancelling the effect of perpendicular components of torque necessary torque will be created and hence axis becomes steady. So the perpendicular components of torque should not be considered in mind.
In short, for the calculation of torque following matters should not keep in mind.
(1) We need to consider only those forces that lie in planes perpendicular to the axis.
(2) We need to consider only those components of the position vectors which are perpendicular to the axis.