As you round corners, you can brake at the same time you make a hard turn to launch into a drift. While you are drifting, your nitro meter will gradually refill. You can refill it even while you're in the process of boosting. Therefore, a good technique is to boost just ahead of a turn, then immediately start drifting through the turn while your boost is going. This will have the effect of allowing you to drift much further distances, since your nitro-consuming boost is counteracted by the bonus you receive for drifting.