Note: You must have version 1.1 patch for the following codes to work.

Mission Select:
Start a new game and enter your name as TheWorldIsYours, then double click on it and then click scenario.

Cheat Mode:
Start a new game and enter your name as TheGalaxyIsYours, then double click on it. Now enter the following during play:

Code                 Result 
M                    500 Command Points
SHIFT + M            500 Command Points and Order Any Unit 
CTRL  + W            Win the Mission 
CTRL  + 8            Show Active Units 
CTRL  + SHIFT + 8    Show All Units 
CTRL  + 9            Remove Fog of War 

Double Unit Carriers:
When a unit carrier explodes, remove the unit at the same time it explodes. If you timed it right, that unit will have doubled.

Front Line Movement Trick:
During a Skirmish battle take control of your opponent's Command Center. As the bomb timer begins to move, click your Reinforcement Screen. You'll find you can bring down anything right outside your opponent's front door! That includes A-I, A-A, and A-V Turrets! The thing is though that you can usually only bring one of each dropship down, so choose what turret you use wisely. (Note: This is only useful if you opponent has control of supply bunkers and has the ability to bring other command center down.)