"For this problem I like to start with what is easiest first. Try tightening the pedals..."

Try removing, cleaning, greasing and then correctly torquing the pedals; I use pedal washers as well. This will catch not only loose pedals but those with debris in the threads and mating surfaces, another common cause of clicking.

Swapping the pedals with another pair will also help eliminate the pedals themselves as sources of the noise; swapping with platform pedals will also help eliminate clip and cleat noises.