SETUP: When pulling off a round house cut back, the key to being successful is generating as much speed as possible before starting the maneuver. Get a few pumps up and down the face to make sure you're movin' at the right speed.
INITIAL TURN: This move actually starts on your bottom turn. Make sure you don't draw out your bottom turn to much or you will loose much of your speed in the flats. Conversely, don't make it too tight or you will be jammed in the pocket of the wave with no space to make a turn. Make a gently arching radius while keeping your weight centered over the mid section of the board.
TRANSITION: As you you come off your bottom turn and start your incline up the wave and out on to the shoulder. Keep the board flat on the face of the wave as to not loose any speed. Once you feel the speed of the board slightly start slowing, begin your turn. Keep you head pointed in the direction you want to go. Your heels should push down to make the inside rail create traction. On a frontside roundhouse you should be looking over your leading shoulder as you move through the turn. Always remember that where your head and shoulders point is where the board will end up moving. Your weight should slightly be focused on the tail of your board in the middle of the turn which will help you push water.
REBOUND: Once you have completed the turn, you will be facing back towards the wave. You have to make a decision at this point. Where should I rebound off the wave? If you make your way up to the crest, you will be force to pull a re-entry to get back into the wave. If you aim for the bottom you might not have enough power to rebound you back onto the shoulder. There is a delicate balance of where to aim. I recommend trying to ride on the inside of the foam ball to regain speed and rebound. Once you are propelled back out on to the shoulder set up to do another roundhouse.
Here is a good video of this move slowed down so you can see the specific movements described above.