Coins
When coins appear on the sides of the road, tilt your device to have your car lean in that direction to collect them. At times you will also have to navigate around obstacles and hazards on the road that can end your run. Large numbers of coins are also awarded for completing missions.
Drifting
To time your drifts, watch for the sparks to appear from your car's muffler. Anticipate their appearance in order to not start your drift too late. If you tap after they appear, you will miss your opportunity. You have to initiate your drift immediately when the sparks are going to appear. If done correctly, the camera will zoom in for a stunt shot. When pulling out of a drift, wait until your car is almost straight with the road. Releasing too early will have your car end up crooked, and miss the accompanying the speed boost. If you release too late, you will hit the wall, damage your car, and lose speed. The more perfect drifts you complete, the higher your drift chain and the faster your overall time will be.
Upgrades
Spend your coins on upgrading your cars to get better drift boosts, faster top speeds, and better durability. Then use your upgraded car to get coins easier and save them for a new car.