There are two predominant schools of thought concerning the rider inputs that cause a motorcycle to turn. The Freddie Spencer school of thought holds that the rider’s position on the
motorcycle is key. Spencer’s arch-rival, Keith Code, runs something called California Superbike School. Code's position is that counter-steering: handlebar pressure alone- is what makes motorcycles turn.
At the Spencer school, they tend to rely on what your prof called “argument from authority" back in Philosophy 101. Freddie, they point out at every opportunity, is a triple World Champion; who ever heard of Keith Code? But over at the California Superbike School, they’ve gone the gadget route. They've created a motorcycle with dual controls. It has one conventional set, and a second handlebar rigidly mounted to the fuel tank. "Think you can body steer?" they sneer, "see how far you get on this.”
As usual in such political debates, once you've studied both positions, you realize they are making essentially the same case, though they see it from opposing perspectives. Each chooses to ignore their similarities, and focus on their differences.
Strip the rhetoric away, and you'll initiate a turn the same way, no matter where you learn to do it. At the approach of the turn, you shift your weight forward and to the inside. Most good riders take care of this early, because it gets awful busy very soon. As you reach the turn-in point, you will simultaneously transfer as much weight as possible to the inside, by hanging off the bike. At this point, the weight of your body is carried by the inside foot-peg, and by the outside knee, which is pressing against the side of the fuel tank (For simplicity, I've left out all the braking and downshifting that accompany most turns, and throttle control which is essential to balance turning forces between front and rear tires).
Then, magic happens. You push on the inside handlebar. Momentarily, you actually steer opposite to the direction you want to travel. This causes the motorcycle to fall down into a
stable lean angle, matched to the radius of the bend and your speed. Your knee makes contact with the pavement, which is usually incidental but serves as a gauge of just how fast you're going. (At this point you must be looking up through the corner, planning your exit, and you couldn't look at the speedometer even if you had one.)
Riding Man Mark Gardiner p176-7