If you are playing a car race game, buy a steering wheel and pedal combo. You don't drive a car with a joystick in real life, so why try to drive one on your Xbox.

Either way, remember that throttle is not ON or OFF. Its progressive just like a gas pedal in a car. You can ease into it to avoid spinning your tires and losing traction. You can also pulse the throttle around corners and get a feel of when the car is sliding. This will give you a better throttle feel on exit of the turn.

Virtual cars (most games) don't break when you pound through the gears. Use the gearing to adjust speed and torque to the wheels before a corner and through the exit. Remember when you lose traction while accelerating simply up-shift to a higher gear and the car will stick.

Similar idea goes for braking, if you need to stop faster, down-shift hard while braking (power brake).

Although the developers go out of their way to simulate real world environments, you can still manipulate the virtual rules to control the car the way you want!