To choose any missiong, go to the SINGLE PLAYER GAME screen and type "drdeath." Click on the Cavedog bone (below the Load Game button) to choose your starting mission.

To add up to 10 AI opponents in Skirmish Mode, go the Skirmish Setup screen and type * plus a Roman numeral for the number of opponents you wish to add. For example, "*iv" will add four AI opponents.

To share resources with your allies in skirmish mode, press ENTER, type one of the codes below, then press ENTER again.

+shareenergy        Shares energy
+sharemetal         Shares metal
+sharemapping       Shares map information

You can control the amount of metal and energy you share by placing a number after these commands. For example, +setshareenergy 2000 will ensure you have at least 2000 energy units at all times.

While playing in Skirmish mode, press ENTER then press the + key and type in the code for the desired effect:

ATM - Gives you 1000 metal and energy. 
CDSTART - Starts CD Music. 
CLOCK - Adds an in-game clock in the corner of the screen. 
CONTOUR# - Displays a 3D contour, # = 1-15. 
CONTROL# - Lets you to control a different skirmish AI. 
DITHER - Changes line-of-sight shading
DOUBLESHOT - All weapons do twice the damage
HALFSHOT - All weapons do half the damage
ILOSE - Causes you to lose
IWIN - Causes you to win
KILL# - Kills off a player, where # is 0-4
NOENERGY - Drops your energy to 0
NOMETAL - Drops your metal to 0
NOSHAKE - Stops explosion screen shakes
NOWISEE - Full map and disables line of sight
RADAR - 100% radar coverage
SING - Makes units "sing" when given orders. 
SHOOTALL - Units will automatically target enemy buildings
SWITCHALT - Lets you switch between squads with # keys instead of ALT-# keys
VIEW# - Display other players' metal and energy.

Build an air transport and have it load up the enemies commander (can usually only be done early in a skirmish against the computer). Fly the commander over the enemies base and self-destruct the air transport. It will nuke the base!