Cheat mode:
Enter the options screen, then select "Cheat Codes". 
Enter one of the following case-sensitive codes:

Effect - Code 
Unlock all modes - theparrot  
Unlock all cities - griswold  
All cities, vehicles and modes in arcade mode - upupdowndown or rimbuk 
Set difficulty, 0 is easiest - howhardcanitbe(0-9)  
Set speed, 0 is slowest - howfastcanitbe(0-9)  
Press F to fire gun, disable damage - starpower 
Press F to fire gun, H to fire rocket, disable damage - leatherandlace 
Press F to fire gun, H to fire rocket, damage not disabled - operationdoom 
Psychedelic view - starlite  
Nitrous - octane 
Unlimited nitrous, also added to bikes - yerbamate 
Faster in-air controls - tumbler  
Reset faster after crash - quickFix  
Unknown - aquaspark 
Unknown - happyhour 

Unlock Motorcycle:
Defeat five motorcycles in a long race. 

Unlock Los Angeles police car:
Win all the circuit races in Los Angeles in arcade mode. 

Unlock Paris police car:
Win all the circuit races in Paris in arcade mode. 

Unlock Tokyo police car:
Win all the circuit races in Tokyo in arcade mode. 

Unlock SLF450X:
Win all the races in Los Angeles, Paris, and Tokyo in arcade mode to unlock the 
SLF450X. It is the fastest car in the game and can hit 250 mph with no boost. You 
can only use it in arcade mode.

Unlock Veloci:
Win all six of the World Champion's races (Savo). 

Wheelie:
If you have the Veloci, you can do a wheelie by going onto two wheels and 
pressing both brakes until you turn around. Then, press the gas to do a wheelie. 
Using nitro while doing the wheelie will help keep you in it.

The best motorcycle to use to practice wheelies is the first one you unlock in 
career mode. This bike is most useful for going down straightaways on the 
highway on the Los Angeles level. If you use the fastest motorcycle instead of this 
bike, you will most likely fall off immediately. 

Slip stream turbo:
Line up in the wake of the car ahead of you, watching air streams and listening for 
the draft noise. Stay in this sweet spot for a few moments until the meter fills up 
with red, and then press [Nitro] to slip ahead of your opponents. Note: You cannot 
use this until you defeat three people in career mode. 

Losing the police:
When side by side with a police car, find a tree or pole ahead that is on the side 
nearest to the police car. Push the police car into the tree or pole. 

When a police car is directly behind you, find a tree or pole ahead. Drive directly 
toward it and when near, take a sharp turn away from it. The police car will smash 
into the tree or pole. 

Two-wheel driving:
This move is much more effective if you pop up on the wheels early, then hold the 
position (hold [Weight Transfer]) and steer your car. If you wait until you are 
about to hit someone, it will not be as easy to see where you should go.

Burnouts:
With some of the cars, you can charge up the burnout faster by revving up the 
engine, then pressing [Handbrake]. It depends on the car, but some will work 
better this way

Spin-out competitors:
As you approach another car from behind, try to line up the front half of your car 
with the back end of the other car. As you touch the back end, turn sharply toward 
the other car. If done correctly, you can make them swerve into a wall or even do 
a 180 and be left behind in the dust.

Motorcycle turns:
If you are making a sharp turn, try to make your wheels hit the wall/building. If 
you use the handbrake or regular brake, you can turn the bike sideways and let 
your wheels hit instead of hitting it head-on. This allows you to stay on the bike 
and keep going. You can also still steer while popping a wheelie. After you pull 
back, keep holding [Weight Transfer] (but stop pulling back) and use the steering 
to move while gaining speed. The view is a little difficult, but you can get a lot of 
speed this way.

Graffiti:
Look at some of the graffiti on the walls in Los Angeles to find some interesting 
things. Near a wall by the airport is graffiti that says "Vice City", referring to the 
fact that Rockstar made both Midnight Club 2 and Grand Theft Auto: Vice City. 
There is also saw a wall that had "Rockstar" on it. 

Go to the dry trench in Los Angeles. You will see graffiti on the sloped part of the 
trench. You can find the names of other Rockstar games such as Grand Theft 
Auto: Vice City and M.C. (Midnight Club).

Paris: Secret area:
Find the Cathedral. Once there, you will see the doors. They appear as if you 
cannot go through them. However, you can drive straight into them and they will 
open, allowing your car to go through.

Tokyo: Big jump:
Select cruise mode and follow your way through the glass rectangle about 50 
meters in front of you. Drive straight until you get to the road up to the freeway. 
Go up onto the freeway and stay on the right-hand side. Take the first turnoff on 
the right. Follow that until it goes back down on the street. You should be next to a 
large river. Follow that river road until you reach a massive jump. You can use it 
and land on the other side of the river. Note: It is best to get a run up from down 
that small street with one of the best cars with some nitro.

Easy wins in Capture The Flag mode: 
Get the item, stop, and allow one of your opponents to get the flag. Then, go all 
the way to the finish line and stay there. When your opponent is racing down to 
the finish line, quickly use stop on his or her car. While stuck there, ram into their 
car, get the flag, and bring it to the finish line. Note: This trick may not work if not 
executed properly. Also. to avoid your opponent's attacks, get a shield or stealth. 

Easy wins in Circuit races:
Enable the "Nitrous" and "Guns and rockets" codes. Use a motorcycle of your 
choice. At the beginning of the race, use the "Burnout" strategy and face a car in 
front of you. You can either use the machine gun to blow it up or use the rockets 
to move them out of your way. If they get past you in any part of the race, fire the 
machine gun and steer and accelerate and fire rockets to knock them off course.

Last Man Standing, The Final Race: 
After you have completed the game and have become the Tokyo champion, 
another message appears. It reads "The World Champion Of Illegal Street 
Racing". However, you are not really the champion until you defeta Shave. He has 
all Velocis and they have five nitros. The best way to defeat him is to enable 
the "All cars" code. Red and yellow Velocis will attempt to run you off the road.

Repair damage and restore nitro: 
When cruising in in career mode with damage and no nitro, find a racer and flash 
your lights at him. Do not follow him. Instead, either stay where you are or drive 
in the opposite direction. Ignore the countdown. Once out of time, your damage 
and nitro will be as if you just started the level.

Flip the finger:
Choose the motorcycle and go into any mode. Remain idle without moving. After 
about thirty seconds, the man on the bike will turn around and flip the finger.