Get 1,500 respect points from all CPU characters.

Complete the all the series in Arcade Mode, except the Extreme Nitrous Series, to unlock the Bronze, Silver, and Gold Prototype Challenge Series.

Get a 100% completion in career mode to unlock prototype mods for all cars in career mode and the Extreme Nitrous Series in Arcade Mode.

Arcade bonuses:
Complete the all the series in Arcade Mode, except the Extreme Nitrous Series, to unlock the Bronze, Silver, and Gold Prototype Challenge Series.

In career mode, go to your garage and do something with one of your cars (for example, switch a part or get a different paint job). The game should autosave. Then, go back to your race menu. Go in a sprint and bet all your money on one car that looks the fastest. It it does not win at least three races out of four, turn off the Xbox and turn it back on. It will load your last autosave. Try the same sprint again until you win then find a different sprint and start the entire process again.

Select the "Cheat" option at the menu.

Extra Money - CASH
Unlock All Arcade Mode Cars - PINT
Everyone Respects You - RESP
Unlock All Cars - CARS
Full Crew - CREW
Character Test Mode - CHAR
Win all races - WIN.
Activate all codes - ALL.

Buy a car and let one of your crewmembers drive it in a race three times (if he is winning them) or four times (if he is not winning). The fastest way is a 2-lap circuit race on your own track.