Build anywhere: Build sandbags from one of your buildings to where you want to build, and build next to the sandbags. Then, sell the sandbags.

Extra cash bug: When you sell three refineries right after each other, the money you get keeps going up until the end of the mission.

Surprise attack: To catch your opponent off guard, build (and charge) an Iron Curtain. Then place it in the midst the enemy, on a structure or tank.