Start the game and get in control of the player or vehicle. The 
cheats will only work when the movement keys are usable.
Now just type in the code on your keyboard:

Code           Result
---------------------------------
trickedout   - Upgrade all weapons by 1 level.
freeman      - Get 5 more lives.
boostershot  - Recover (life) energy faster.
bombsaway    - Get 20 more grenades.
microwave    - Get 20 more nukes.
fastforward  - Skip to the next Zone (there are 5 Zones in total).

Note: That the game will know you are cheating and not award any Medals
at the end of a Level.