i would suggest practicing the shimmy slowly at first on one foot, then the other and picking up speed as long as technique is correct. then i'd recommend holding unto a barre or wall, and practicing the same on the balls of your feet, and then on one foot (while still on releve) and then the other. correct technique is key here, and more than anything, having full control of whichever shimmy speed you choose. you may then want to add level changes and walking with it (flat footed and on the balls of the feet). though you may have a really good 3/4 by itself right now, its always good to go back to basics to make sure that its not a technique issue...

once this is nice and strong, *slowly* add the undulation, again at first flat footed, then on one foot, then releve on both feet, then releve on one foot--adding level changes for good measure. holding unto a barre can be helpful as you really focus on the movement rather than balance, etc. make sure the undulation is small and controlled--at least at first--again, correct technique and posture are key here.

besides this, its all about practice... :) good luck!!!

In addition to working from the detailed technique direction (working up slowly as Marta explained so well), you may also want to try loosening it up.

One of the issues I see with students trying to layer the 3/4 shimmy over anything else is that they often are over-controlling the 3/4 shimmy. That is, they're working so hard on the hips that the upper body becomes tense in order to not also shake along with the lower body. Obviously that makes an Arabic hard to layer over the shimmy. If you're having this problem, spend some time working with the 3/4 shimmy at full speed as simply a bounce-step on each hip, making sure the body is relaxed & the upper body can do other things (for instance make arm gestures, brush your hair, pick up your pet, etc.). THEN add the Arabic, the Turkish Shimmy forward/back step, the Ghawazee Shimmy swing, etc.

Thankyou ladies that is great! Hopefully i'll be less of a disaster zone for next weeks class!!!
Off to practice :)
x Katie