I have often watched master fly casters and marveled at how they were able to cast so smoothly, even when they are casting long distances. Many experienced casters could be great casters if they could just figure out how to achieve that smoothness. Here's a quick tip to help you smooth out the lumps in your cast.
Apply the correct amount of power and apply the power evenly - Many experienced fly fishers overpower their forward casts in an attempt to gain distance and actually send detrimental shock waves into the line or worse, cause a tailing loop by overloading the rod too early in the stroke.
To correct this - Get out on the lawn or on a pond with no fish around and practice casting with the absolute minimum amount of power necessary applied to your forward cast to make it straighten out. With some practice and adjustments you'll find that you are able to smooth out your cast by applying less power and, with the power applied smoothly and evenly, you will actually find that you are able to cast farther with less effort.
Remember that your stops still need to be deliberate and your pauses between strokes need to be long enough to allow the line to straighten. If you get out there and practice this simple technique you should be able to smooth out those shock waves and then proceed to practice applying more and more power, but applying it without shock waves.