Note: This procedure involves editing a game file; create a backup copy of the file before proceeding. Use a text editor to edit the "skrimish.ini" file in the "C:\Documents and Settings\User\Application Data\Command & Conquer 3 Tiberium Wars\Profiles\ProfileName" directory. Change the "10000" number of starting credits to any desired number.
Scrin campaign
Successfully complete the GDI and NOD campaign to unlock the four mission Scrin campaign.
Hold more Tiberium without Tiberium Silos
Note: This was done with the v1.4 patch. You can increase the amount of Tiberium you can have without the Tiberium Silos. When it asks you to build a Tiberium Silo, just build something, and when it completes just cancel (preferably something expensive like a Tech Center). The amount of Tiberium you can hold keeps increasing every time you do this.
GDI attack combinations
The following are attack combinations you can use in Skirmish missions:
Pitbull
Predator Tank
APC with a Grenadier Squad inside
3 or more Rifleman Squads
3 or more Missile Squads
2 APCs with Rifleman Squads inside
2 APCs with Missile Squads inside
2 Grenadier Squads
2 Rifleman Squads
2 Missile Squads
NOD attack combinations
The following are attack combinations you can use in Skirmish missions:
2 Militant Squads
2 Militant Rocket Squads
4 Raider Buggys
2 Flame Tanks
2 Scorpion Tanks
4 Raider Buggys
2 Attack Bikes
SCRIN attack combinations
The following are attack combinations you can use in Skirmish missions:
4 Buzzers
4 Disintergrators
3 Seekers (combined with Buzzers)
3 Gun Walkers (combined with Buzzers)
Play as NOD in Skirmish mode (demo version)
At the Skirmish options menu, hold N and click your army to unlock NOD as a selectable option. To switch back to GDI, hold G and click your army. This also works for the CPU army.