Unlock Hints:
Ending bonuses: Complete the game to unlock the Free Run mode (no vehicles on the road), Free Run Twin mode (two player Free Run), and the "Credits" options. 
Unlock Face Off mode: Complete championship mode 

Unlock Vehicles: 
Unlock these vehicles by beating them in Face Off mode
Face Off 1: Roadster
Face Off 2: Towtruck
Face Off 3: Saloon GT
Face Off 4: Bus 

Quick start: 
Accelerate immediately before the "1" fades during the pre-race countdown to get a slight speed boost. 

Full bonus: 
Drive a perfect lap (no accidents) and your bonus will be automatically filled.