Disc - Mega Build
In Episode 6 of the Zerg "Brood War" campaign, rescue the two Zerg hives on the first level, then look in one of the first level's corners for a data disc. Grab this disc to activate the "Mega Build" cheat, allowing you to instantly build structures.
White Flag - Fog of War
In Episode 3 of the Protoss "Brood War" campaign, go to the small island near your starting point. Touch the white flag on this island to activate the "Fog of War" cheat. This cheat will remove the fog of war, allowing you to see the entire game map.
Ursadon - Minerals and Gas
In Episode 1 of the Terran "Brood War" campaign, locate the computer beacon in the room with four civilians. Use the bottom door to exit. Move to the right and defeat the fire bats in the next area. Locate the Ursadon being held in a cell and send in a Marine to talk to it. Move all your units into the cell when it asks to be hugged and press the "B" button to activate the "Minerals and Gas" cheat. Whenever you activate this cheat, you will receive 1,000 minerals and gas.
Orange Civilian - All Upgrades
In Episode 1 of the original Terran campaign, move Jim Raynor into the first main room and then the northern hallway. This hall will branch off, so move Raynor through the right hallway and approach the Orange Civilian. If you do not shoot this person, he will talk to you and tell you to follow him. Do so until he disappears to receive the "All Upgrades" cheat. This will allow you to build any unit or building you want at the beginning of the match.