This page features two photos of the same waterfall using two different techniques. My favorite approach for waterfalls is to use a long exposure. The main difference is the texture of the water, which is controlled by the shutter speed. However, the other settings (aperture and ISO) work together to allow the use of a faster or slower shutter speed. As shown below, using a smaller aperture (larger f/stop number) and a lower ISO will allow the use of a slower shutter speed.
I also used a neutral density (ND) filter to achieve the long exposure. ND filters reduce the amount of light passing through the camera lens, allowing the use of longer shutter speeds. The photo on the right was taken with a 6 stop ND filter (linked here). Using a slow shutter speed will obviously also require the use of a tripod, and a remote shutter release is very helpful to avoid camera shake.
I'm not saying this is the best or only way to shoot waterfalls, but I enjoy it. I hope this page helps you learn this technique. My settings for each photo are listed below. If you require any further assistance, feel free to contact me.