When should you downshift on a motorcycle?

Downshifting puts the motorcycle in a lower gear to access more power for the engine's current RPM. Reasons to downshift: to accelerate (downshift before passing on highway, then accelerate); when slowing down significantly (downshift before braking heavily, so engine braking helps and you are in the right gear for restart); when climbing a steep hill; when the engine starts to lug (run below comfortable RPM). Downshift smoothly: pull in the clutch, click the shifter down once, blip the throttle to match engine speed (avoiding rear-wheel lockup), release the clutch smoothly. Multiple downshifts at high speed need throttle matching to prevent the rear wheel from locking up due to compression braking.