The key to drifting is in the amount of speed you can control while cornering with precision. To drift you have to start driving at high speed while you start to break in a corner and when you see that it starts to turn a corner, you have to apply the handbrake with the circular button, so that the rear wheels slide. Just make sure you keep the momentum
Keep sliding around the corner, then turn in the opposite direction to regain control and finish the drift.