Proper steering technique means being "quiet" with the handlebars except for those forces
Handlebars have a purpose: They turn the bike when you apply pressure to them.
They're also the de facto home to four of our six controls, conveniently located so our hands can work the throttle, front brake and clutch. Problems arise from using the handlebars for purposes other than those intended. Riders routinely confuse themselves with improper, complicated and conflicting bar inputs.
For example, when rolling through a series of switchbacks, consider the potential inputs a rider might make in his transitions from side to side:
1) Some torso weight may be supported on the bars, especially if there is any deceleration between turns.
2) The rider inputs steering pressure to flick the bike back and forth.
3) Unless it is a series of ever-increasing-radius turns, the rider is rolling the throttle on and off.
4) In aggressive riding positions, (read: hanging off), a rider helps himself across the bike by using the bars as a leverage point, rotating torque on the bars.
5) The rider changes gears in a way that requires additional throttle and possibly clutching.
6) The rider may pull himself forward on the bike to prevent sliding too far back in the seat.
7) Or he may hold himself back, creating forward pressure on the bars similar to supporting himself under braking.
A graph of all these inputs creates three separate torque vectors applied to the bars at once. Each opposes the other, making their execution difficult. Consider the downforce from braking, torso support or pulling forward (points 1, 6 and 7 above). That pressure counters bar rotation for steering (2). Consider also the rotational torque from using the bars as a pivot to move our butts over (4). This makes all of the above difficult and energy-consuming. Essentially we have forces in conflict with one another.
Meanwhile, riders are trying to be accurate with throttle inputs because that timing is critical for smooth riding. Steering is equally critical to success in esses and linked corners. Transitions are easily mistimed with these contradictory inputs. All of this can result in an overactive suspension, a missed line and difficult steering. Forward weight transfer that helps turn the bike may have the opposite effect when done too early or too late. On top of all this, the effort can be exhausting, resulting in sore muscles.
As we transition from one side to the other, there is yet another complication: The bike becomes light as it swings over the top of its roll arc. Exaggerated inputs at this point are notorious for causing pronounced twitching or headshake, especially when the bike is under acceleration. Should a wheelie happen in this scenario, any fork rotation can bring about serious effects like a full-on tank-slapper all the way to the front contact patch auguring in and flicking the back around: the dreaded high-side.
The usual solutions for any of these distracting effects are to slow down or apply more effort to the situation, but the conflicting nature of the forces negates applying more ergs of energy as a viable solution. Better timing of the control inputs can improve it. Moving over in the seat prior to the next steering change can eliminate the rotational torque happening simultaneously with the steering inputs. That puts the rider in a better position to steer the bike. Gear changes can be done earlier or later. Using tank-grip pads to help maintain a stable position on the bike can offer some mechanical improvement.
In the end, though, each rider has an optimum position on the bike for making these inputs without the strain and pain. Correct positioning of the controls-peg height fore, aft and vertical; seat height, tilt and length; bar rotation in and out-is essential. Spending money on adjustable rearsets can make a world of difference in fit.
While the mechanical aspects may all be set correctly for the rider, it is no guarantee he'll be purposeful and in control with his inputs. The right timing and positioning isn't something most riders achieve in a single day. Track training, with spot-on coaching, is still the quickest way to achieve one's own goals of comfort, stability and that elusive quality of smoothness.