If its not a low pitch, or happens at certain point in a whole crank spin, then I think it could be your pedals, but without actually hearin gthe sound its difficult for me to say. However, random with a slightly high sounding click, is generally your pedals. The noise will be the bearings in them. Putting WD40 is not what you want to do, as this is actually a de-greaser. It may get rid of the noise a little bit, but will later come back again. You want to be able to get into the bearings and grease them. But rememeber not all pedals are possible to seperate every part.