By Peugeot UK rally driver Kris Meeke:
There's sliding a car, and there's power sliding a car - and in a rear or early four-wheel-drive car the first one loses you time and the second, if done correctly, can gain you time.
Power sliding successfully is a mental thing as much as a physical one. You have to understand what the car is doing - and be one step of ahead of it, so you can provoke it to do what you want to do next. You can't afford to be reacting to the car's movements, as that means it's controlling you, not the other way round.
In a powerful rear-wheel drive car you can essentially steer on the throttle, to the point that you steer with your right foot and then react with the steering wheel. You get the car into the slide with the power and then control its extent by steering against the direction of travel - opposite lock. You still need to be smooth with your inputs, though - going from lock to lock and whacking the throttle will never work.
How much power you have is also crucial. An old Gp B car like the Metro 6R4 had 600bhp or more that lt out its power in big bursts, plus relatively crude brakes and suspension - finding the balancing point where you can control a power slide in one of those cars is a real art.