Begin braking with your right foot as you approach the corner. Use the ball of your foot to apply pressure to the brake pedal. This provide the optimal brake pressure since the ball of your foot is aligned with your knee.
Placing the ball of your foot in the center of the brake pedal will allow the right side of your foot to hang off the brake pedal and be closer to the gas pedal. This will be important for the next few steps.
Press in the clutch pedal with your left foot.
While still applying pressure to the brake pedal with your right foot, roll your foot to the right so that you touch the gas pedal. Use the outside edge of your right foot to press and release or "blip" the throttle. This will briefly raise the engine's RPM to match the speed of the wheels and ensure a smooth shift. Only practice will help you figure out the precise amount of throttle blip required in your car, but you can try between 1,000 to 2,000 RPM to downshift a single gear.
Move the shift lever into the gear that you want to select. This is usually one gear lower that the gear you were in prior to braking.
Let out the clutch with your left foot.
Take your right foot off the brake and turn into the corner. Accelerate smoothly out of the corner in the correct gear.