With a good map this is quite easy. Simply follow any river (usually a blue line)
‘till is crosses an area where the contour (height) lines are bunched together. The
only other thing to do is to make sure that you approach the area from the low side
as most waterfalls are almost invisible from upstream. For the smaller waterfalls
(really just fast moving water) any place that a river travels over rocky ground
is a good bet, especially if there are lots of contour lines in the area as well.