I'm going to disagree with
@mgmine on two points. There are lots of opinions out there on how to build water features, so feel free to ignore me, but I have watched a lot of pros on YouTube and have picked up a few things along the way:
1. you'll never see a professional pond builder use the stair steps method to build a waterfall. With very few exceptions (generally due to space constraints) they will start at the bottom and build to the top. At each level you repeat the same steps: frame boulder on the right, frame boulder on left, some kind of weir rock in between. You start with your general height and berm spread and build the falls to fit the rocks, not vice versa. As you build up the falls, you are either digging out or backfilling to make the space fit the rock, not vice versa. At each level your goal should be to create some level of pooling behind the rocks - bigger pool means bigger falls. You can pinch openings or spread them out to get the desired effect. Tighter space to pass through makes water appear to be bigger and faster.
2. You need the OPPOSITE of a lot of rocks. The fewest, biggest rocks possible make the most natural looking water feature. A lot of rocks just looks like, well, a lot of rocks. Check out any of the professionals on Youtube that have been recommended in this thread and you'll see what I mean. Aquascape, Tussey, Modern Design, Atlantis - they're all putting out tons of great content for free. They will literally tell you every tip and trick they use to build natural looking features. No reason in the world not to take advantage of what they're offering.
One last suggestion - and again, beauty is in the eye of the beholder. But you will rarely see a stream cut straight down a hill. Instead they will meander back and forth, twisting and turning. Water is looking to avoid obstructions and find the easiest path - rocks or logs or other physical obstacles in the way will just create another turn. Some of the falls will face toward you but others will face away and you'll just see the water as it twists around.