Before changing pedals, identify the L and R markings. Viewed from outside the bicycle, the right pedal tightens clockwise and the left counterclockwise. When using a hex key from behind the crank, the apparent direction of rotation reverses.
Grease the pedal threads and follow the specific model’s instructions for final tightening. For example, Shimano specifies 35–55 N·m for the PD-EH510; that range should not automatically be applied to every pedal.
Start the thread by hand. If it binds, stop and check alignment instead of adding force. Have the correct tool and model instructions ready before working, and ask a workshop to assess uncertain or damaged threads.