Originally Posted by JARblue

If you're not talking about the rear tires actually losing traction, it is most likely you are experiencing roll (sway bars are probably the best bang for the buck here).

If you are losing the rear end and that's not your goal, it sounds to me like you are entering the corner incorrectly (driving course is probably best bang for the buck here). When I want to loosen the rear end, I would describe it as "throwing" the car into the turn - jerk the wheel and get on the throttle. Racing through a turn is completely different and all about the apex of the turn. As many have said, "smoothness" is key; you would never jerk the wheel at any point during the turn.