Well it does come down to personal preference but I do think people are being short changed when it come to natural rock pools and creeks. Unless you know what is possible then it is quite natural to be excited by a hose squirting out from under a rock and if you choose to ignore the concrete or black pond liner that is often visible. What would you rather see? The plumbing on display or a pond and waterfall that looks like its always been there and that keeps people guessing as to how it works? You want to be transported back to nature by your pond.
Stacking the edge with rock above ground level as a sort of after-though that leaves the liner visible to the water line.
Using all one size of stone or boulder. There should be a good natural mix of stone from 150mm to 600mm minimum and in a 1:2:1 ratio, the 2 being 200 to 400 mm majority. The pebble on the bottom and the edges should also vary in size.
Making the single waterfall too high for an area or topography. Keep it in proportion.
Also it is best to have them as near as possible to your outdoor socialising areas or visible from you living areas. They do become part of the family.