Well keep reading as I am about to explain the simple things that will get you great shots with no problem at all.
First you will need to have 2 elements of nature in your favour, one is that is has to be overcast, or the whites in the water will be over exposed for you and once you loose detail there is no way you will get it back. Second is there has to be water flowing, I have tracked to many falls, get there and there is nothing at all.
So once you are at a waterfall, you will then need to have your camera mounted on a tripod as exposures will be too long to hand hold and you will avoid any camera shake. The only other piece of equipment I have for these shots are a polarising filter, this will take any glare that is on the greenery and any highlights that are in the water as well. Once I am there I will generally take my light meter and take an exposure of anything that is green, be it a fern or leaves that are in your frame should be surfice.
Another aspect to take into consideration is colour balance, sometimes if you in shade at a waterfall and its sunny day but before 10am, then it will give you a cold colour temp and have a very blue effect, to avoid that all you need to do is change your colour balance from auto to shade, this will give you a warmer shot before any sun hits the falls and your time there is up.
With your exposures, if you have an exposure of 1 second or more, you will get the smooth flow of the water as you can see in this photo of Curtis Falls, the filter will help you get slower shutter speeds as you will need to adjust by 1-2 stops of light in your camera.
I hope this has given some incite into what I do and how I achieve it. But the best way to learn is to get out there and take photos.