How does a wizard control a broomstick?

Question

My question is how does a wizard control a broomstick? How does he/she make it go forward, make it go faster, left/right, etc.? Is that all done with the mind or also movements of your body? And, in addition to that, how can one wizard be a better flyer than someone else?

Answer 1

Leaning forward (pointing the broom downwards) causes the broom to descend.

‘Keep your brooms steady, rise a few feet and then come straight back down by leaning forwards slightly. On my whistle – three – two –’

_{^{Harry Potter and the Philosopher's Stone}}

The opposite also seems to be true.

He pulled his broomstick up a little to take it even higher and heard screams and gasps of girls back on the ground and an admiring whoop from Ron.

_{^{Harry Potter and the Philosopher's Stone}}

Leaning your body forward (and grasping the broom to prevent if from pointing downwards) causes the broom to accelerate.

Harry knew, somehow, what to do. He leant forward and grasped the broom tightly in both hands and it shot towards Malfoy like a javelin.

_{^{Harry Potter and the Philosopher's Stone}}

Pulling the broom straight appears to both brake and level the broomstick.

... he stretched out his hand – a foot from the ground he caught it, just in time to pull his broom straight, and he toppled gently on to the grass with the Remembrall clutched safely in his fist.

_{^{Harry Potter and the Philosopher's Stone}}

Turning seems to be accomplished by gripping the shaft of the broom and tugging it in one direction or another.

And at long last, Harry mounted his Firebolt, and kicked off from the ground. It was better than he’d ever dreamed. The Firebolt turned with the lightest touch; it seemed to obey his thoughts rather than his grip. It sped across the pitch at such speed that the stadium turned into a green and grey blur; Harry turned it so sharply that Alicia Spinnet screamed, then he went into a perfectly controlled dive, brushing the grassy pitch with his toes before rising thirty, forty, fifty feet into the air again –

_{^{Harry Potter and the Prisoner of Azkaban}}

and

He lost track of time. It was getting harder and harder to hold his broom straight. The sky was getting darker, as though night had decided to come early. Twice Harry nearly hit another player, without knowing whether it was a team-mate or opponent; everyone was now so wet, and the rain so thick, he could hardly tell them apart …

_{^{Harry Potter and the Philosopher's Stone}}

Answer 2

In regards to how can someone be better at flying a broomstick than others I would imagine it would be similar to how one can be better at driving a car or motorcycle. Response time would play a large part in it as well as having better hand eye coordination (ie knowing how much to turn and how fast you can go while turning so that you don't turn too wide and hit a brick wall)