Type them at the frontend of the Game or pause the race and type in
 the cheats:

 MACHTHREE  - a new car with max speed of 600 km/h
 IMPACT     - unlimited ammo in deathmatch
 OVERKILL   - weaponmode in championship
 ALLOFF     - cheats off
 LIKEPAMELA - tuning phase 5 for all systems
 CLEMENTINE - free choice in starting league
 MCCOY      - animated switches in the menus
 LISELOTTE  - all addtional systems on 99
 NALICE     - all cars available

 BUGGYBOY   - Debug mode with ...

              A - Autopilot youre car drives allone (besttimes)
              F - Displays Framerates
              G - Switch between the cars (be sure that you have
                  pressed A before)
              I - Informations system
              P - Sreenshoot
              W - Fix the car