When you appreciate your implant moving
start with letting your surgeon know of your concerns. There are some strategies that may help minimize it from moving but if the pocket is too large and there was not adherence of the capsule to the implant, I don't think there is much that you can do to prevent further rotation. If it happens again, another procedure will be needed and consideration could be given towards using the product with the most aggressive texturing in the future. But there has been some speculation that the most aggressive texturing can contribute towards developing anaplastic lymphoma.
If a breast implant has moved and the deformity is mild, I would wait and see if you could live with it. If not, you may need another revision or consider choosing a round implant, when it moves, it looks the same.
I assume that the implant is a shaped mentor textured implant. These implants can rotate if the pocket created is larger than the implant. If rotation is happening then would see your plastic surgeon and after exam get his/her recommendations. If the rotation is obvious then would require surgery to make the pocket snug to the implant. Would include partial capsulectomies and use of acellular matrix. If tissue ingrowth is absent then a total capsulectomy may be needed.