Enter the following codes at the Main Menu.

All Circuit tracks:
Down, R, R, R, Black, Black, Black, X

All Drag tracks:
Left, X, Right, R, X, L, White, Black

All Drift tracks:
Right,, Right, Right, Right, Left, Black, R, White

All Sprint tracks:
Up, Black, Black, Black, R, Down, Down, Down

Drift physics for all cars:
R, Up, Up, Up, Down, Down , Down, L

Hints

Unlock Samantha's Car:
Earn enough Style points to obtain every Vinyl. After that you will need to fill the Style meter again and you will receive her car.

Thanks to Revolution readers Corey Matthews and Grapeape!